Patent Publication Number: US-2022221439-A1

Title: Systems and methods for determining concentrations of mobile hydrogen of metallic objects and/or reducing concentrations of mobile hydrogen of metallic objects

Description:
FIELD 
     The subject matter disclosed herein generally relates to systems and methods for determining concentrations of mobile hydrogen of metallic objects (e.g., in and/or on surfaces of the metallic objects). The subject matter disclosed herein also relates to systems and methods for reducing concentrations of mobile hydrogen of metallic objects (e.g., in and/or on surfaces of the metallic objects). 
     BACKGROUND 
     In many industries, such as the aerospace industry, significant reliance is placed on high strength steel (“HSS”) and titanium alloys for critical applications. However, HSS and titanium alloys (and metals more generally) are susceptible to hydrogen embrittlement, which is a complex process that is not completely understood, but which can lead to sudden and/or severe failure of metallic components. Hydrogen embrittlement of metals can occur whenever and wherever metals are exposed to atomic or molecular hydrogen including, for example, various acids or water. The source of such exposure can be, for example, internal hydrogen embrittlement (e.g., carbonizing, casting, electroplating, heat treating, and/or welding) or hydrogen environmental embrittlement (e.g., galvanic corrosion, general corrosion, and/or exposure to chemicals or soils). 
     One example of internal hydrogen embrittlement is electroplating (e.g., with cadmium or zinc) of metallic components for corrosion protection. Because the electroplating process is not 100% efficient, some of the associated current applied goes into dissociation of water molecules (H 2 O) into free hydrogen (e.g., H), hydrogen molecules (H 2 ), and oxygen molecules (O 2 ). Free hydrogen and/or hydrogen molecules generated on surfaces of the HSS and/or titanium alloys can be trapped in place, for example, by the deposition of metal ions on those surfaces during electroplating. If not removed, this free hydrogen (e.g., in ionic form) and/or hydrogen molecules can then diffuse interstitially into the HSS and/or titanium alloys and cause hydrogen embrittlement. 
     Some hydrogen in metallic components (whether or not electroplated) can be removed through the application of temperature over time. Hydrogen in metallic components that can be removed through the application of temperature over time, without melting the metallic components, is referred to as “mobile hydrogen”. 
     Generally, in the application of temperature over time, as the time is increased, the temperature can be decreased and vice versa. However, in a manufacturing process, both time and temperature have associated costs, necessitating careful business, engineering, production, and other decisions. 
     A standard technique for reducing and/or removing such mobile hydrogen is to bake the electroplated metallic components in an air oven at high temperature (e.g., 375° F.) for a specified minimum period of time (e.g., 24 hours). For example, values of minimum baking time at 375° F. for different types of steels can be found in Heat Treatment of Steel Parts—General Requirements (AMS 2759). 
     This standard technique adds time and complexity, and increases costs associated with manufacturing of the electroplated metallic components. In addition, porosity of the electroplating affects the baking process because as plate porosity decreases, the efficiency of the baking process at removing mobile hydrogen also decreases. 
     Applicant notes that not all mobile hydrogen in metallic objects can be removed by such baking processes (e.g., nondestructive testing using heat for a specified minimum period of time). The mobile hydrogen that cannot be reduced or removed in this way can be removed by melting the metallic object. However, melting the metallic objects is a destructive testing method that can defeat the original purpose of the testing process. 
     For assessing the health of such metallic components with respect to hydrogen embrittlement (e.g., to ensure that the baking of the electroplated metallic components was effective), many industries, such as the aerospace industry, currently rely on periodic (e.g., weekly or monthly) testing of witness coupons that were electroplated in the same tanks as the metallic components, but not at the same time. Further, such witness coupons are electroplated only on a periodic basis, not with every batch of electroplated metallic components. As a result, the health of specific metallic components can only be inferred from the testing results of the witness coupons (e.g., witness coupons are only surrogates for the actual metallic components). 
     In addition, each test of witness coupons can take, for example, from 200 hours up to 10 days to complete (e.g., per the methodology of ASTM International F519—Standard Test Method for Mechanical Hydrogen Embrittlement Evaluation of Plating/Coating Processes and Service Environments). For this reason, production hardware is often released for use in manufacturing—with significant control, monetary, process, and other risks—pending completion of testing of the associated witness coupons. 
     Because of the issues discussed above, there is a need in many industries, such as the aerospace, automotive, defense, electronics, maritime, and rail-transport industries, for faster testing of such metallic components and for testing of the actual metallic components themselves, as opposed to the testing of witness coupons. 
     The disclosures of U.S. Pat. No. 3,426,579 to Lebel et al. (“Lebel”) and U.S. Pat. No. 3,783,678 to Das et al. (“Das”) are incorporated in the present application by reference. 
     SUMMARY 
     The present disclosure is directed to analytical inspection systems for determining concentration of mobile hydrogen of metallic objects (e.g., in and/or on surfaces of the metallic objects), analytical inspection methods for determining concentration of mobile hydrogen of metallic objects (e.g., in and/or on surfaces of the metallic objects), systems for reducing concentration of mobile hydrogen of metallic objects (e.g., in and/or on surfaces of the metallic objects), and/or methods for reducing concentration of mobile hydrogen of metallic objects (e.g., in and/or on surfaces of the metallic objects). 
     In some examples, an analytical inspection system for determining concentration of mobile hydrogen of a metallic object can comprise: a vacuum furnace; a hydrogen sensing device; and/or a flow path from the vacuum furnace to the hydrogen sensing device. The hydrogen sensing device can be configured to detect and/or measure the mobile hydrogen at levels less than or equal to 1 part per million (ppm). 
     In some examples of the analytical inspection system, the vacuum furnace can comprise a heating subsystem. 
     In some examples of the analytical inspection system, the vacuum furnace can comprise a cooling subsystem. 
     In some examples of the analytical inspection system, the vacuum furnace can comprise a carrier gas subsystem. 
     In some examples of the analytical inspection system, the vacuum furnace can comprise a pump subsystem configured to reduce pressure inside the vacuum furnace to less than about 1×10 −6  Torr. 
     In some examples of the analytical inspection system, the hydrogen sensing device can comprise a hydrogen detector or hydrogen analyzer. 
     In some examples of the analytical inspection system, the analytical inspection system can be configured to cause a flow of the mobile hydrogen out of the vacuum furnace in one direction. 
     In some examples of the analytical inspection system, the analytical inspection system can be configured to cause a flow of the mobile hydrogen out of the vacuum furnace in a first direction or in a second direction different from the first direction. 
     In some examples of the analytical inspection system, the hydrogen sensing device can comprise a mass spectrometer. 
     In some examples of the analytical inspection system, the metallic object can be an aerospace object. 
     In some examples of the analytical inspection system, the aerospace object can be an airplane part. 
     In some examples of the analytical inspection system, the vacuum furnace can comprise a pump subsystem configured to reduce pressure inside the vacuum furnace to less than about 1×10 −4  Torr and greater than about 1×10 −10  Torr. 
     In some examples of the analytical inspection system, the vacuum furnace can comprise a heating subsystem configured to raise temperature inside the vacuum furnace to greater than or equal to 100° F. and less than or equal to 1,000° F. 
     In some examples of the analytical inspection system, the vacuum furnace can comprise: a pump subsystem configured to reduce pressure inside the vacuum furnace to within a pressure band that is less than about 1×10 −4  Torr and greater than about 1×10 −10  Torr; and a heating subsystem configured to raise temperature inside the vacuum furnace to within a temperature band that is greater than or equal to 100° F. and less than or equal to 1,000° F. The pump subsystem and the heating subsystem can be configured to maintain the pressure band and the temperature band for greater than or equal to 0.5 hours and less than or equal to 50 hours. 
     An analytical inspection method for determining concentration of mobile hydrogen of a metallic object can comprise: placing the metallic object into a vacuum furnace; drawing a vacuum in the vacuum furnace; and/or simultaneously heating the metallic object in the vacuum furnace and measuring a quantity of the mobile hydrogen released from the metallic object using a hydrogen sensing device. The hydrogen sensing device can be configured to detect and/or measure the mobile hydrogen at levels less than or equal to 1 ppm. 
     In some examples of the analytical inspection method, measuring of the quantity of the mobile hydrogen released from the metallic object can comprise: drawing a sample from the vacuum furnace; and/or providing the sample to the hydrogen sensing device. 
     In some examples of the analytical inspection method, the hydrogen sensing device can comprise a hydrogen detector or hydrogen analyzer. 
     In some examples of the analytical inspection method, the analytical inspection method can cause a flow of the mobile hydrogen out of the vacuum furnace in one direction. 
     In some examples of the analytical inspection method, the analytical inspection method can cause a flow of the mobile hydrogen out of the vacuum furnace in a first direction or in a second direction different from the first direction. 
     In some examples of the analytical inspection method, the hydrogen sensing device can comprise a mass spectrometer. 
     In some examples of the analytical inspection method, the metallic object can be an aerospace object. 
     In some examples of the analytical inspection method, the aerospace object can be an airplane part. 
     In some examples of the analytical inspection method, the drawing of the vacuum in the vacuum furnace can comprise reducing pressure inside the vacuum furnace to less than about 1×10 −4  Torr and greater than about 1×10 −10  Torr. 
     In some examples of the analytical inspection method, the heating of the metallic object in the vacuum furnace can comprise raising temperature inside the vacuum furnace to greater than or equal to 100° F. and less than or equal to 1,000° F. 
     In some examples of the analytical inspection method, pressure inside the vacuum furnace can be reduced to within a pressure band that is less than about 1×10 −4  Torr and greater than about 1×10 −10  Torr, temperature inside the vacuum furnace can be raised to within a temperature band that is greater than or equal to 100° F. and less than or equal to 1,000° F., and/or the pressure band and the temperature band can be maintained for greater than or equal to 0.5 hours and less than or equal to 50 hours. 
     In some examples, a system for determining concentration of mobile hydrogen of a metallic object can comprise: a vacuum furnace; a hydrogen sensing device; and/or a flow path from the vacuum furnace to the hydrogen sensing device. The hydrogen sensing device can be configured to detect and/or measure the mobile hydrogen at levels less than or equal to 1 part per million (ppm). 
     In some examples of the system, the vacuum furnace can comprise a heating subsystem. 
     In some examples of the system, the vacuum furnace can comprise a cooling subsystem. 
     In some examples of the system, the vacuum furnace can comprise a carrier gas subsystem. 
     In some examples of the system, the vacuum furnace can comprise a pump subsystem configured to reduce pressure inside the vacuum furnace to less than about 1×10 −6  Torr. 
     In some examples of the system, the hydrogen sensing device can comprise a hydrogen detector or hydrogen analyzer. 
     In some examples of the system, the analytical inspection system can be configured to cause a flow of the mobile hydrogen out of the vacuum furnace in one direction. 
     In some examples of the system, the analytical inspection system can be configured to cause a flow of the mobile hydrogen out of the vacuum furnace in a first direction or in a second direction different from the first direction. 
     In some examples of the system, the hydrogen sensing device can comprise a mass spectrometer. 
     In some examples of the system, the metallic object can be an aerospace object. 
     In some examples of the system, the aerospace object can be an airplane part. 
     In some examples of the system, the vacuum furnace can comprise a pump subsystem configured to reduce pressure inside the vacuum furnace to less than about 1×10 −4  Torr and greater than about 1×10 −10  Torr. 
     In some examples of the system, the vacuum furnace can comprise a heating subsystem configured to raise temperature inside the vacuum furnace to greater than or equal to 100° F. and less than or equal to 1,000° F. 
     In some examples of the system, the vacuum furnace can comprise: a pump subsystem configured to reduce pressure inside the vacuum furnace to within a pressure band that is less than about 1×10 −4  Torr and greater than about 1×10 −10  Torr; and a heating subsystem configured to raise temperature inside the vacuum furnace to within a temperature band that is greater than or equal to 100° F. and less than or equal to 1,000° F. The pump subsystem and the heating subsystem can be configured to maintain the pressure band and the temperature band for greater than or equal to 0.5 hours and less than or equal to 50 hours. 
     In some examples, a method for reducing concentration of mobile hydrogen of a metallic object can comprise: placing the metallic object into a vacuum furnace; drawing a vacuum in the vacuum furnace; heating the metallic object in the vacuum furnace; measuring a quantity of the mobile hydrogen released from the metallic object using a hydrogen sensing device; and/or continuing the heating of the metallic object in the vacuum furnace until the measured quantity of the mobile hydrogen released from the metallic object is below a threshold value. The hydrogen sensing device can be configured to detect and/or measure the mobile hydrogen at levels less than or equal to 1 ppm. 
     In some examples of the method, the measuring of the quantity of the mobile hydrogen released from the metallic object can comprise: drawing a sample from the vacuum furnace; and/or providing the sample to the hydrogen sensing device. 
     In some examples of the method, the hydrogen sensing device can comprise a hydrogen detector or hydrogen analyzer. 
     In some examples of the method, the method can cause a flow of the mobile hydrogen out of the vacuum furnace in one direction. 
     In some examples of the method, the method can cause a flow of the mobile hydrogen out of the vacuum furnace in a first direction or in a second direction different from the first direction. 
     In some examples of the method, the hydrogen sensing device can comprise a mass spectrometer. 
     In some examples of the method, the metallic object can be an aerospace object. 
     In some examples of the method, the aerospace object can be an airplane part. 
     In some examples of the method, the drawing of the vacuum in the vacuum furnace can comprise reducing pressure inside the vacuum furnace to less than about 1×10 −4  Torr and greater than about 1×10 −10  Torr. 
     In some examples of the method, the heating of the metallic object in the vacuum furnace can comprise raising temperature inside the vacuum furnace to greater than or equal to 100° F. and less than or equal to 1,000° F. 
     In some examples of the method, pressure inside the vacuum furnace can be reduced to within a pressure band that is less than about 1×10 −4  Torr and greater than about 1×10 −10  Torr, temperature inside the vacuum furnace can be raised to within a temperature band that is greater than or equal to 100° F. and less than or equal to 1,000° F., and/or the pressure band and the temperature band can be maintained for greater than or equal to 0.5 hours and less than or equal to 50 hours. 
     In some examples of the method, the threshold value can be 1 ppm. 
     In some examples of the method, the heating of the metallic object in the vacuum furnace can be continued until the measured quantity of the mobile hydrogen released from the metallic object is reduced by 50%. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the present teachings, as claimed. 
    
    
     
       DRAWINGS 
       The above and/or other aspects and advantages will become more apparent and more readily appreciated from the following detailed description of examples, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  shows an analytical inspection system for determining concentrations of mobile hydrogen of metallic objects (e.g., in and/or on surfaces of the metallic objects), according to some examples of the disclosed apparatuses; 
         FIG. 2  shows a vacuum furnace, according to some examples of the disclosed apparatuses; 
         FIG. 3  shows an analytical inspection system for determining concentrations of mobile hydrogen of metallic objects (e.g., in and/or on surfaces of the metallic objects), according to some examples of the disclosed apparatuses; 
         FIGS. 4A and 4B  show analytical inspection systems for determining concentrations of mobile hydrogen of metallic objects (e.g., in and/or on surfaces of the metallic objects), according to some examples of the disclosed apparatuses; 
         FIG. 5  shows an analytical inspection method for determining concentrations of mobile hydrogen of metallic objects (e.g., in and/or on surfaces of the metallic objects), according to some examples of the disclosed methods; and 
         FIG. 6  shows a method for reducing concentration of mobile hydrogen of metallic objects (e.g., in and/or on surfaces of the metallic objects), according to some examples of the disclosed methods. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary aspects will now be described more fully with reference to the accompanying drawings. Examples of the disclosure, however, can be embodied in many different forms and should not be construed as being limited to the examples set forth herein. Rather, these examples are provided so that this disclosure will be thorough and complete, and will fully convey the scope to a person having ordinary skill in the art (“PHOSITA”). In the drawings, some details may be simplified and/or may be drawn to facilitate understanding rather than to maintain strict structural accuracy, detail, and/or scale. For example, the thicknesses of layers and regions may be exaggerated for clarity. 
     It will be understood that when an element is referred to as being “on,” “connected to,” “electrically connected to,” or “coupled to” to another component, it may be directly on, connected to, electrically connected to, or coupled to the other component or intervening components may be present. In contrast, when a component is referred to as being “directly on,” “directly connected to,” “directly electrically connected to,” or “directly coupled to” another component, there are no intervening components present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, and/or section from another element, component, region, layer, and/or section. For example, a first element, component, region, layer, or section could be termed a second element, component, region, layer, or section without departing from the teachings of examples. 
     Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” and the like may be used herein for ease of description to describe the relationship of one component and/or feature to another component and/or feature, or other component(s) and/or feature(s), as illustrated in the drawings. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation(s) depicted in the figures. 
     The terminology used herein is for the purpose of describing particular examples only and is not intended to be limiting of examples. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as understood by a PHOSITA. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     The present disclosure is directed to systems for determining concentrations of mobile hydrogen of metallic objects (e.g., in and/or on surfaces of the metallic objects). 
       FIG. 1  shows an analytical inspection system for determining concentrations of mobile hydrogen of metallic objects (e.g., in and/or on surfaces of the metallic objects), according to some examples of the disclosed apparatuses. 
     As shown in  FIG. 1 , analytical inspection system  100  can comprise: vacuum furnace  102 ; hydrogen sensing device  104 ; and/or flow path  106  from vacuum furnace  102  to hydrogen sensing device  104 . Thus, analytical inspection system  100  is configured to cause a flow of mobile hydrogen out of vacuum furnace  102  in one direction. 
     Impetus for flow through analytical inspection system  100  is an overall pressure difference across analytical inspection system  100 , with the highest pressure at vacuum furnace  102 , pressure decreasing from vacuum furnace  102  toward hydrogen sensing device  104 , and the lowest pressure at hydrogen sensing device  104 . Such an overall pressure difference can be caused, for example, by one or more vacuum pumps (not shown) downstream from hydrogen sensing device  104 . The one or more vacuum pumps can comprise, for example, one or more turbomolecular pumps. 
     One or more metallic objects can be placed into vacuum furnace  102 , for example, immediately following the completion of an electroplating process. After placement of the one or more metallic objects into vacuum furnace  102 , vacuum furnace  102  can be sealed and an initial vacuum drawn in vacuum furnace  102 . While the initial vacuum is drawn, vacuum furnace  102  can be isolated, for example, from flow path  106  and hydrogen sensing device  104  by one or more valves (not shown). 
     The one or more metallic objects in vacuum furnace  102  simultaneously can be heated and a quantity of mobile hydrogen released from (e.g., desorbed from outer surfaces of) the one or more metallic objects. This quantity of mobile hydrogen released from and/or present on surfaces of the metallic object can be measured using hydrogen sensing device  104 . Flow path  106  provides a route for the mobile hydrogen released from the one or more metallic objects to get from vacuum furnace  102  to hydrogen sensing device  104 . Effectively, a stream of mobile hydrogen stripped from outer surfaces of the one or more metallic objects passes through hydrogen sensing device  104 , where the mobile hydrogen is measured. 
     In some examples of the analytical inspection system, the hydrogen sensing device can comprise a hydrogen detector or hydrogen analyzer. 
     Hydrogen sensing device  104  can utilize one or more analytical techniques, such as electron capture, flame ionization, gas chromatography, mass spectrometry, or thermal conductivity. For example, hydrogen sensing device  104  can comprise a mass spectrometer. Such a mass spectrometer can use, for example, a previously developed correlation curve to determine the quantity of mobile hydrogen released from the metallic object based on the measurements made by the mass spectrometer. Such analytical techniques are known to a PHOSITA. 
     In some examples of analytical inspection system  100 , hydrogen sensing device  104  is capable of detecting and/or measuring mobile hydrogen at levels less than or equal to 1 ppm, at levels less than or equal to 500 ppb, at levels less than or equal to 200 ppb, at levels less than or equal to 100 ppb, at levels less than or equal to 50 ppb, at levels less than or equal to 25 ppb, at levels less than or equal to 10 ppb, or at levels less than or equal to 5 ppb (e.g., 1 ppb). As such, the systems and methods of the present application represent a significant improvement over state-of-the-art hydrogen analyzers, at least some of which require exacting procedures for creating test specimens; which measure surface hydrogen, bulk hydrogen (e.g., hydrogen filled voids), and total hydrogen, but not mobile hydrogen, using the test specimens; and/or which destructively test (via melting) the test specimens. 
       FIG. 2  shows a vacuum furnace, according to some examples of the disclosed apparatuses. As known to a PHOSITA, such a vacuum furnace can be, for example, a hot-wall design or a cold-wall design. 
     As shown in  FIG. 2 , vacuum furnace  202  can comprise: vacuum chamber  208 ; radiation shields/insulation  210 ; and/or heating subsystem  212 . Vacuum furnace  202  can be connected to hydrogen sensing device  204  via flow path  206 . 
     Vacuum chamber  208  can be, for example, a carbon steel or stainless steel cylindrical shell, typically closed at one end with an access door at the opposite end for loading/unloading of the one or more metallic objects and other uses (e.g., cleaning). The access door can comprise, for example, an autoclave-style locking ring. 
     Vacuum chamber  208  should be capable of withstanding significant pressure differences between an interior of vacuum chamber  208  and an exterior of vacuum chamber  208  (e.g., atmospheric pressure), whether the pressure is higher in the interior or higher on the exterior. Hence, vacuum chamber  208  can be of rugged design including, for example, thick-wall construction, double-wall construction, internal ribs, and/or external ribs. Because of this rugged design and associated multiple subsystems, vacuum chamber  208  typically costs much more (e.g., by a factor of about 10) than an air oven of comparable volumetric capacity. 
     Radiation shields/insulation  210  can define, for example, a hot zone associated with vacuum furnace  202 . Effectively, the hot zone is the volume within radiation shields/insulation  210 . The hot zone can be referred to, for example, as a graphite hot zone, in which radiation shields/insulation  210  typically comprise graphite (e.g., multiple layers of graphite felt), or an all-metal hot zone, in which radiation shields/insulation  210  typically comprise molybdenum and/or stainless steel (e.g., molybdenum and/or stainless steel sheet metal). 
     As design considerations, graphite is hygroscopic and graphite hot zones generally heat more slowly that all-metal hot zones. 
     Heating subsystem  212  can comprise, for example, electrical resistance heating elements comprising, for example, graphite, molybdenum, tantalum, and/or tungsten. In a graphite hot zone, the heating elements of heating subsystem  212  can comprise graphite. In an all-metal hot zone, the heating elements of heating subsystem  212  can comprise molybdenum. 
     Heating subsystem  212  can comprise, for example, a plurality of heating elements spaced circumferentially around vacuum chamber  208  and longitudinally down the length of vacuum chamber  208 . For purposes of temperature uniformity within the hot zone, the heating elements of heating subsystem  212  can be spaced in a relatively uniform manner circumferentially and longitudinally. 
     As a design consideration, because graphite hot zones generally heat more slowly that all-metal hot zones, a graphite hot zone of heating subsystem  212  can require more heating elements and/or higher capacity heating elements than an all-metal hot zone. 
     The one or more metallic objects can be placed inside a volume generally defined by the heating elements of heating subsystem  212 , inside of radiation shields/insulation  210 , and inside of vacuum chamber  208 . 
     Initially, the temperature in vacuum furnace  202 , when vacuum furnace  202  is opened (e.g., to offload a previous batch of the one or more metallic objects and/or to load a subsequent batch of the one or more metallic objects), can be equal to ambient temperature. However, a PHOSITA would understand that during processing, when vacuum furnace  202  is opened, residual heat in vacuum furnace  202  can cause the temperature in vacuum furnace  202  to be higher than ambient temperature. 
     Initially, the pressure in vacuum furnace  202 , when vacuum furnace  202  is opened, can be equal to ambient pressure. Once the one or more metallic objects are loaded into vacuum furnace  202 , the access door can be closed and a vacuum drawn in vacuum furnace  202 . 
     Generally, pressure at hydrogen sensing device  204  can be maintained at a vacuum (e.g., so that pressure P hsd  at hydrogen sensing device  204  satisfies: 1×10 −10  Torr≤P hsd ≤1×10 −4  Torr, 1×10 −7  Torr≤P hsd ≤1×10 −5  Torr, or 1×10 −7  Torr≤P hsd ≤1×10 −6  Torr). While vacuum furnace  202  is opened (e.g., at ambient pressure), hydrogen sensing device  204  can be isolated using one or more isolation valves (not shown in  FIG. 2 ). 
     Once the vacuum is drawn in vacuum furnace  202  such that the pressure in vacuum furnace  202  is approximately equal to the pressure at hydrogen sensing device  204 , the one or more isolation valves can be opened. 
     During or after a vacuum is drawn in vacuum furnace  202 , heating subsystem  212  can raise the temperature in vacuum furnace  202  to one or more temperatures within a range appropriate for the material of the one or more metallic objects. Thus, the time during which the vacuum has been drawn in vacuum furnace  202  is generally greater than or equal to the time during which heating subsystem  212  raises and maintains the temperature in vacuum furnace  202  within the range appropriate for the material of the one or more metallic objects. 
     For material of the one or more metallic objects comprising aluminum and/or aluminum alloys (aluminum alloyed with, for example, one or more of chromium, copper, iron, magnesium, manganese, silicon, titanium, vanadium, zinc, zirconium, or other element(s)), for example, the heating subsystems can raise the temperature in the vacuum furnace to greater than or equal to 77° F. and less than or equal to 1,200° F.; greater than or equal to 200° F. and less than or equal to 500° F.; or greater than or equal to 275° F. and less than or equal to 375° F. 
     For material of the one or more metallic objects comprising steels (iron and carbon alloyed with, for example, one or more of aluminum, boron, chromium, cobalt, copper, manganese, molybdenum, nickel, niobium, phosphorous, silicon, sulfur, titanium, tungsten, vanadium, zirconium, or other element(s)), for example, the heating subsystems can raise the temperature in the vacuum furnace to greater than or equal to 77° F. and less than or equal to 5,000° F.; greater than or equal to 100° F. and less than or equal to 1,000° F.; or greater than or equal to 250° F. and less than or equal to 550° F. For example, a temperature of about 285° F. could be appropriate for carburized low-alloy steels, while a temperature of about 500° F. could be appropriate for some high-hardness bearing steels. 
     For material of the one or more metallic objects comprising titanium and/or titanium alloys (titanium alloyed with, for example, one or more of aluminum, chromium, cobalt, copper, iron, manganese, molybdenum, nickel, niobium, nitrogen, oxygen, tantalum, vanadium, zirconium, or other element(s)), for example, the heating subsystems can raise the temperature in the vacuum furnace to greater than or equal to 77° F. and less than or equal to 3,000° F.; greater than or equal to 150° F. and less than or equal to 750° F.; or greater than or equal to 200° F. and less than or equal to 400° F. 
     Per Fick&#39;s laws of diffusion, raising the temperature of one or more metallic objects in the vacuum furnace will increase the diffusion of mobile hydrogen toward outer surfaces of the one or more metallic objects. This is particularly true because, during the heating, the vacuum furnace will be hotter than the one or more metallic objects. Thus, the one or more metallic objects will be hotter on outer surfaces than within the interior, so the driving force of the diffusion of mobile hydrogen will tend to favor diffusion toward the outer surfaces. 
     As also shown in  FIG. 2 , vacuum furnace  202  can further comprise: pump subsystem  214 ; cooling subsystem  222 ; optional carrier gas subsystem  238 ; and/or sampling subsystem  246 . 
     As shown in  FIG. 2 , pump subsystem  214  can comprise first line  216  connecting vacuum chamber  208  to first vacuum pump  218 . Generally, the direction of flow in first line  216  is defined by first arrow  220 . 
     First vacuum pump  218  can comprise, for example, a cryopump, an ion-getter pump, a mechanical booster pump, a liquid sealing pump, an oil diffusion pump, a rotary pump, a titanium sublimation pump (e.g., with one or more titanium filaments), and/or a turbomolecular pump. 
     In order to quickly draw a strong vacuum in vacuum chamber  208 , a motor associated with first vacuum pump  218  can be quite large (e.g., hundreds of horsepower or kilowatts). 
     As a design consideration, the capacity of first vacuum pump  218  can be driven by the size of vacuum chamber  208 , the expected gas load when the initial vacuum is drawn, and/or the level of vacuum to be drawn in vacuum chamber  208 . 
     As another design consideration, because graphite is hygroscopic, a graphite hot zone can require a more powerful first vacuum pump  218  than an all-metal hot zone. 
     In some examples of vacuum furnace  202 , first vacuum pump  218  can lower the pressure inside vacuum chamber  208  to less than or equal to about 1×10 −3  Torr, less than or equal to about 1×10 −4  Torr, less than or equal to about 1×10 −5  Torr, less than or equal to about 1×10 −6  Torr, less than or equal to about 1×10 −7  Torr, less than or equal to about 1×10 −8  Torr, less than or equal to about 1×10 −9  Torr, less than or equal to about 1×10 −19  Torr, or less than or equal to about 1×10 −11  Torr (e.g., so that the pressure P s  at the suction of first vacuum pump  218  satisfies: 1×10 −19  Torr≤P s ≤1×10 −4  Torr, 1×10 −7  Torr≤P s ≤1×10 −5  Torr, or 1×10 −7  Torr≤P s ≤1×10 −6  Torr). Such pressures can be measured, for example, by ionization gauges (not shown). 
     The time required for first vacuum pump  218  to lower the pressure inside vacuum chamber  208  depends, for example, on the interior volume of vacuum furnace  202  and associated piping, and the presence of flow restrictions (if any); on the type, size, and power of first vacuum pump  218 ; and on the desired pressure. The time required can be as short as five minutes or as long as an hour. Shorter or longer times can be envisioned depending upon circumstances (e.g., problems with continuity of power, system leaks, unusually large or small interior volume of vacuum furnace  202 ). 
     First vacuum pump  218  can remove air, oxygen, and other gases from the vacuum furnace. Such removal can reduce or prevent convective heat loss from one or more metallic objects in vacuum furnace  202 , contamination of the one or more metallic objects, and/or oxidation of the one or more metallic objects. 
     As discussed above, a standard technique for removing mobile hydrogen from an electroplated metallic component is to bake the electroplated metallic component in an air oven at high temperature (e.g., 375° F.) for a specified minimum period of time (e.g., 24 hours). So, the baking by the air oven also takes advantage of Fick&#39;s laws of diffusion. However, in the air oven, the mobile hydrogen that diffuses to surfaces of the electroplated metallic component generally combines with oxygen molecules (O 2 ) in the air oven to form water molecules (H 2 O), which is an exothermic reaction, and the water molecules subsequently evaporate due the temperature in the air oven. Thus, there is a thermodynamic driving force behind the removal of this mobile hydrogen. 
     In contrast, in vacuum furnace  202 , the mobile hydrogen that diffuses to surfaces of the electroplated metallic component is stripped away from those surfaces due to the vacuum in vacuum furnace  202 . This vacuum-related driving force behind the removal of this mobile hydrogen is stronger than the thermodynamic driving force associated with the air oven. And the required time at temperature in vacuum furnace  202  can be significantly shorter than that for baking in an air oven. For example, the required time at temperature in vacuum furnace  202  can be greater than or equal to 15 minutes and less than or equal to about 150 hours (e.g., 100 hours), greater than or equal to 30 minutes and less than or equal to about 50 hours (e.g., 48 hours or 2 days), greater than or equal to 45 minutes and less than or equal to about 25 hours (e.g., 24 hours or 1 day), or greater than or equal to 1 hour and less than or equal to about 2 hours (e.g., 2 hours). For example, the required time at temperature in vacuum furnace  202  can be about 5 hours, about 4 hours, about 3 hours, about 2 hours, or about 1 hour. Thus, although the testing of witness coupons can take up to 200 hours, the present application can provide direct results from the one or more metallic objects in about 24 hours or fewer, and the results can be obtained during or after the one or more metallic objects is at pressure and temperature in vacuum furnace  202 . 
     The systems and method of the present application can be used in tandem with hydrogen removal operations (e.g., a hydrogen-relief bake) or in a quality assurance process (e.g., after a hydrogen-relief bake). In addition, the systems and method of the present application can be used during Original Equipment Manufacturing (“OEM”) or during overhaul/remanufacturing operations. 
     Therefore, the present application also provides systems and methods for reducing time at temperature requirements for reducing the hydrogen concentration of metallic objects. In addition, the present application provides systems and methods for increasing the efficiency and/or effectiveness of reducing hydrogen embrittlement in metallic objects. 
     Moreover, the present application eliminates the need for witness coupons in hydrogen embrittlement testing, and the associated problems with periodic testing of such witness coupons. Instead, the present application allows assessment of hydrogen-embrittlement-related data directly from the actual metallic objects for which such data is sought. 
     As shown in  FIG. 2 , cooling subsystem  222  can comprise second line  224  connecting vacuum chamber  208  to fan  226 , third line  228  connecting fan  226  to heat exchanger  230 , and fourth line  232  connecting heat exchanger  230  to vacuum chamber  208 . Generally, the direction of flow in second line  224  is defined by second arrow  234 , and the direction of flow in fourth line  232  is defined by third arrow  236 . 
     In order to quickly cool vacuum chamber  208  and one or more metallic objects inside vacuum chamber  208 , a motor associated with fan  226  can be quite large (e.g., hundreds of horsepower or kilowatts). As known to a PHOSITA, cooling subsystem  222  can shorten process cycle times and/or can act as a gas quench system. 
     In choosing a cooling gas, specific heat capacity and thermal conductivity of the gas can be important considerations. The cooling gas can comprise, for example, argon, helium, or nitrogen. In some examples, the cooling gas can be argon (optionally mixed with helium). 
     Although hydrogen is an acceptable cooling gas for some uses, it is not acceptable for the present application. 
     Gas pressure and gas velocity can be important in cooling subsystem  222 , in which the only cooling mechanism can be convection. The gas pressure can be, for example, 1 bar (about 7.5×10 2  Torr) to 25 bar (about 1.9×10 4  Torr), with the maximum pressure dependent upon the ruggedness of the design of vacuum chamber  208 . 
     Fan  226  can drive the flow of the cooling gas in cooling subsystem  222 . Heat exchanger  230  can be a direct gas-to-water heat exchanger. 
     As shown in  FIG. 2 , optional carrier gas subsystem  238  can comprise fifth line  240  connecting carrier gas supply  242  to vacuum chamber  208 . Generally, the direction of flow in fifth line  240  is defined by fourth arrow  244 . 
     The carrier gas can comprise, for example, argon, helium, or nitrogen. In some examples, the carrier gas can be helium. 
     Although hydrogen is an acceptable carrier gas for some uses, it is not acceptable for the present application. 
     When carrier gas is not used, mobile hydrogen released from the metallic object can leave vacuum chamber  208  via sampling subsystem  246 . When carrier gas is used, mobile hydrogen released from the metallic object can be entrained in the carrier gas, the carrier gas with the entrained mobile hydrogen then leaves vacuum chamber  208  via sampling subsystem  246 . 
     As shown in  FIG. 2 , sampling subsystem  246  can comprise flow path  206  connecting vacuum chamber  208  to hydrogen sensing device  204 . Generally, the direction of flow in flow path  206  is defined by fifth arrow  248 . 
     The relationship of vacuum furnace  202 , hydrogen sensing device  204 , and flow path  206  in sampling subsystem  246  can be similar to the relationship of vacuum furnace  102 , hydrogen sensing device  104 , and flow path  106  in analytical inspection system  100  of  FIG. 1 . 
     In some examples, hydrogen sensing device  204  is capable of detecting and/or measuring mobile hydrogen at levels less than or equal to 1 ppm, at levels less than or equal to 500 ppb, at levels less than or equal to 200 ppb, at levels less than or equal to 100 ppb, at levels less than or equal to 50 ppb, at levels less than or equal to 25 ppb, or at levels less than or equal to 10 ppb, or at levels less than or equal to 5 ppb (e.g., 2 ppb). 
       FIG. 3  shows an analytical inspection system for determining concentrations of mobile hydrogen of metallic objects (e.g., in and/or on surfaces of the metallic objects), according to some examples of the disclosed apparatuses. 
     As shown in  FIG. 3 , analytical inspection system  300  can comprise: vacuum furnace  302 ; flow path  306   a  from vacuum furnace  302  to optional oxygen trap/oxygen scrubber solution subsystem  350 ; flow path  306   b  from optional oxygen trap/oxygen scrubber solution subsystem  350  to optional diffusion barrier subsystem  352 ; and flow path  306   c  from optional diffusion barrier subsystem  352  to hydrogen sensing device  304 . Thus, analytical inspection system  300  is configured to cause a flow of mobile hydrogen out of vacuum furnace  302  in one direction. 
     Impetus for flow through analytical inspection system  300  is an overall pressure difference across analytical inspection system  300 , with the highest pressure at vacuum furnace  302 , pressure decreasing from vacuum furnace  302  toward hydrogen sensing device  304 , and the lowest pressure at hydrogen sensing device  304 . In particular, there can be a significant differential pressure across optional diffusion barrier subsystem  352 . Such an overall pressure difference can be caused, for example, by one or more vacuum pumps (not shown) downstream from hydrogen sensing device  304 . The one or more vacuum pumps can comprise, for example, one or more turbomolecular pumps. 
     In vacuum furnace  302 , hydrogen can be present, for example, in elemental form, as water, and/or in organic material. Given the possibility for gases other than hydrogen to be present (e.g., argon, carbon dioxide, helium, krypton, neon, nitrogen, oxygen, and/or xenon), optional diffusion barrier subsystem  352  can serve as a permeable barrier specific for hydrogen only. Such a barrier can comprise, for example, a heated palladium or palladium-alloy (e.g., palladium-silver alloy or palladium-gold alloy) foil of small cross-sectional area (e.g., heated to about 1,100° F.). In the alternative, such a barrier can comprise a thin non-metallic membrane (e.g., ceramic or glass) as the barrier specific for hydrogen only. As would be understood by a PHOSITA, such a barrier can comprise, for example, one or more scrubbers for various chemical components (e.g., CO 2 , O 2 ) and/or a molecular sieve column. 
     In addition, oxygen tends to react chemically with hydrogen in the presence of a hot metal surface (such as optional diffusion barrier subsystem  352 ) to form water, according to the following exothermic reaction. 
       2H 2 +O 2 →2H 2 O (vapor)
 
     As a result, optional oxygen trap/oxygen scrubber solution subsystem  350  can remove such oxygen prior to optional diffusion barrier subsystem  352  so that the quantity of mobile hydrogen released from the metallic object is actually measured and not lost to water vapor. 
     In this way, optional oxygen trap/oxygen scrubber solution subsystem  350  can comprise a barrier specific for oxygen or oxygen only. Thus, optional oxygen trap/oxygen scrubber solution subsystem  350  can remove any gaseous oxygen from the flow that proceeds from vacuum furnace  302  to hydrogen sensing device  304 . 
     Oxygen traps and oxygen scrubber solutions are known to a PHOSITA. 
     In some examples of the analytical inspection system, vacuum furnace  302  or the flow path from vacuum furnace  302  to hydrogen sensing device  304  can comprise optional diffusion barrier subsystem  352 . 
     Optional diffusion barrier subsystem  352  can comprise a barrier specific for hydrogen only. Such a barrier can comprise, for example, heated palladium, heated palladium alloys (e.g., palladium-silver alloy or palladium-gold alloy), mild steel (e.g., low-carbon steel), nickel, or manganese alloys as the barrier specific for hydrogen only. The barrier can be in the form of a foil. In the alternative, such a barrier can comprise a thin non-metallic membrane (e.g., ceramic or glass) as the barrier specific for hydrogen only. As would be understood by a PHOSITA, such a barrier can comprise, for example, one or more scrubbers for various chemical components (e.g., CO 2 , O 2 ) and/or a molecular sieve column. 
     Optional diffusion barrier subsystem  352  can remove any gases other than mobile hydrogen from the flow that proceeds from vacuum furnace  302  to hydrogen sensing device  304 . 
     In some examples of analytical inspection system  300 , hydrogen sensing device  304  is capable of detecting and/or measuring mobile hydrogen at levels less than or equal to 1 ppm, at levels less than or equal to 500 ppb, at levels less than or equal to 200 ppb, at levels less than or equal to 100 ppb, at levels less than or equal to 50 ppb, at levels less than or equal to 25 ppb, at levels less than or equal to 10 ppb, or at levels less than or equal to 5 ppb (e.g., 3 ppb). 
       FIGS. 4A and 4B  show analytical inspection systems for determining concentrations of mobile hydrogen of metallic objects (e.g., in and/or on surfaces of the metallic objects), according to some examples of the disclosed apparatuses. 
     As shown in  FIG. 4A , analytical inspection system  400   a  can comprise: vacuum furnace  402 ; flow path  406  which splits (e.g., in a first direction) toward isolation valve  454 , hydrogen sensing device  404 , and second vacuum pump  458  and (e.g., in a second direction) toward isolation valve  456  and third vacuum pump  460 . Thus, analytical inspection system  400   a  can be configured to cause a flow of mobile hydrogen out of vacuum furnace  402  in a first direction or in a second direction different from the first direction. 
     Second vacuum pump  458  and/or third vacuum pump  460  can comprise, for example, one or more cryopumps, ion-getter pumps, oil diffusion pumps (with cryogenic traps to minimize backstreaming of pump oil), titanium sublimation pumps, and/or turbomolecular pumps. 
     In some examples of analytical inspection system  400   a , second vacuum pump  458  and/or third vacuum pump  460  can lower the pressure at a suction of the respective pump to less than or equal to about 1×10 −3  Torr, less than or equal to about 1×10 −4  Torr, less than or equal to about 1×10 −5  Torr, less than or equal to about 1×10 −6  Torr, less than or equal to about 1×10 −7  Torr, less than or equal to about 1×10 −8  Torr, less than or equal to about 1×10 −9  Torr, less than or equal to about 1×10 −10  Torr, or less than or equal to about 1×10 −11  Torr (e.g., so that the pressure P s  at the suction of the respective pump satisfies: 1×10 −10  Torr≤P s ≤1×10 −4  Torr, 1×10 −7  Torr≤P s ≤1×10 −5  Torr, or 1×10 −7  Torr≤P s ≤1×10 −6  Torr). Such pressures can be measured, for example, by ionization gauges (not shown). 
     Analytical inspection system  400   a  can be operated with isolation valves  454  and  456  both shut. In this first mode, vacuum furnace  402  would be isolated and the associated first vacuum pump (e.g., similar to first vacuum pump  218  in  FIG. 2 ), for example, could rapidly draw an initial vacuum in vacuum furnace  402 . 
     Analytical inspection system  400   a  can be operated with isolation valve  454  open and isolation valve  456  shut. In this second mode, analytical inspection system  400   a  would operate similar to analytical inspection system  100  of  FIG. 1 , with second vacuum pump  458  reducing pressure at hydrogen sensing device  404  to provide the impetus for flow through analytical inspection system  400   a.    
     Analytical inspection system  400   a  can be operated with isolation valve  454  shut and isolation valve  456  open. In this third mode, analytical inspection system  400   a  can be pumped down to an extremely low pressure to empty flow path  406  all the way back to vacuum furnace  402  in preparation for later operation. 
     In some examples of analytical inspection system  400   a , hydrogen sensing device  404  is capable of detecting and/or measuring mobile hydrogen at levels less than or equal to 1 ppm, at levels less than or equal to 500 ppb, at levels less than or equal to 200 ppb, at levels less than or equal to 100 ppb, at levels less than or equal to 50 ppb, at levels less than or equal to 25 ppb, at levels less than or equal to 10 ppb, or at levels less than or equal to 5 ppb (e.g., 4 ppb). 
     As shown in  FIG. 4B , analytical inspection system  400   b  can comprise: vacuum furnace  402 ; flow path  406  which splits (e.g., in a first direction) toward isolation valve  454 , hydrogen sensing device  404   a , and second vacuum pump  458  and (e.g., in a second direction) toward isolation valve  456 , hydrogen sensing device  404   b , and third vacuum pump  460 . Thus, analytical inspection system  400   b  can be configured to cause a flow of mobile hydrogen out of vacuum furnace  402  in a first direction or in a second direction different from the first direction. 
     Hydrogen sensing device  404   a  and hydrogen sensing device  404   b  can be different devices, or analytical inspection system  400   b  can be designed with a single hydrogen sensing device that effectively can be switched back and forth between the position of hydrogen sensing device  404   a  and the position of hydrogen sensing device  404   b . Either the two-device design or the switchable single-device design can provide significant advantages in flexibility over a single flow path design. 
     Second vacuum pump  458  and/or third vacuum pump  460  can comprise, for example, one or more cryopumps, ion-getter pumps, oil diffusion pumps (with cryogenic traps to minimize backstreaming of pump oil), titanium sublimation pumps, and/or turbomolecular pumps. 
     In some examples of analytical inspection system  400   b , second vacuum pump  458  and/or third vacuum pump  460  can lower the pressure at a suction of the respective pump to less than or equal to about 1×10 −3  Torr, less than or equal to about 1×10 −4  Torr, less than or equal to about 1×10 −5  Torr, less than or equal to about 1×10 −6  Torr, less than or equal to about 1×10 −7  Torr, less than or equal to about 1×10 −8  Torr, less than or equal to about 1×10 −9  Torr, less than or equal to about 1×10 −10  Torr, or less than or equal to about 1×10 −11  Torr (e.g., so that pressure P s  at the suction of the respective pump satisfies: 1×10 −19  Torr≤P s ≤1×10 −4  Torr, 1×10 −7  Torr≤P s ≤1×10 −5  Torr, or 1×10 −7  Torr≤P s ≤1×10 −6  Torr). Such pressures can be measured, for example, by ionization gauges (not shown). 
     Analytical inspection system  400   b  can be operated with isolation valves  454  and  456  both shut. In this first mode, vacuum furnace  402  would be isolated and the associated first vacuum pump (e.g., similar to first vacuum pump  218  in  FIG. 2 ), for example, could rapidly draw an initial vacuum in vacuum furnace  402 . 
     Analytical inspection system  400   b  can be operated with isolation valve  454  open and isolation valve  456  shut. In this second mode, analytical inspection system  400   b  would operate similar to analytical inspection system  100  of  FIG. 1 , with second vacuum pump  458  reducing pressure at hydrogen sensing device  404   a  to provide the impetus for flow through analytical inspection system  400   b.    
     Analytical inspection system  400   b  can be operated with isolation valve  454  shut and isolation valve  456  open. In this third mode, analytical inspection system  400   b  would operate similar to analytical inspection system  100  of  FIG. 1 , with third vacuum pump  460  reducing pressure at hydrogen sensing device  404   b  to provide the impetus for flow through analytical inspection system  400   b.    
     Switching between the second and third modes can allow for faster measurements of the hydrogen concentration of metallic objects in that the quantity of mobile hydrogen released from a first metallic object can be measured using the second mode, then the quantity of mobile hydrogen released from a second metallic object can be measured using the third mode, where the speed of measurements effectively can be reduced to the time required to switch from the first metallic object in the vacuum furnace at vacuum and temperature to the second metallic object in the vacuum furnace at vacuum and temperature. 
     Switching between the second and third modes also can allow for maintenance in the isolated flow path while operating the other flow path. The isolated flow path also can be pumped down to an extremely low pressure to empty that flow path back to the respective isolation valve in preparation for later operation. 
     In some examples of analytical inspection system  400   b , hydrogen sensing device  404   a  is capable of detecting and/or measuring mobile hydrogen at levels less than or equal to 1 ppm, at levels less than or equal to 500 ppb, at levels less than or equal to 200 ppb, at levels less than or equal to 100 ppb, at levels less than or equal to 50 ppb, at levels less than or equal to 25 ppb, at levels less than or equal to 10 ppb, or at levels less than or equal to 5 ppb (e.g., 1, 2, 3, 4, or 5 ppb). 
     In some examples of analytical inspection system  400   b , hydrogen sensing device  404   b  is capable of detecting and/or measuring mobile hydrogen at levels less than or equal to 1 ppm, at levels less than or equal to 500 ppb, at levels less than or equal to 200 ppb, at levels less than or equal to 100 ppb, at levels less than or equal to 50 ppb, at levels less than or equal to 25 ppb, at levels less than or equal to 10 ppb, or at levels less than or equal to 5 ppb (e.g., 1, 2, 3, 4, or 5 ppb). 
       FIG. 5  shows an analytical inspection method for determining concentrations of mobile hydrogen of metallic objects (e.g., in and/or on surfaces of the metallic objects), according to some examples of the disclosed methods. 
     As shown in  FIG. 5 , an analytical inspection method ( 500 ) for determining concentration of mobile hydrogen of a metallic object can comprise: placing the metallic object into a vacuum furnace ( 502 ); drawing a vacuum in the vacuum furnace ( 504 ), as discussed above; and simultaneously heating the metallic object and measuring a quantity of mobile hydrogen released from the metallic object using a hydrogen sensing device ( 506 ), as discussed above. 
     As used herein, “heating” a metallic object includes raising temperature inside the vacuum furnace, into which the metallic object has been placed, to a temperature band above ambient temperature and/or maintaining temperature inside the vacuum furnace, into which the metallic object has been placed, within a temperature band above ambient temperature. 
     The measuring of the quantity of mobile hydrogen released from the metallic object can comprise: drawing a sample from the vacuum furnace; and/or providing the sample to the hydrogen sensing device. 
     Drawing a sample from the vacuum furnace can comprise causing the sample to pass through an optional oxygen trap/oxygen scrubber solution subsystem and/or an optional diffusion barrier subsystem. As discussed above, the optional oxygen trap/oxygen scrubber solution subsystem reduces or eliminates oxygen gas from the sample, while the optional diffusion barrier subsystem selectively passes hydrogen in the sample. 
     Providing the sample to the hydrogen sensing device can comprise causing the sample to pass through an optional oxygen trap/oxygen scrubber solution subsystem and/or an optional diffusion barrier subsystem. As discussed above, the optional oxygen trap/oxygen scrubber solution subsystem reduces or eliminates oxygen gas from the sample, while the optional diffusion barrier subsystem selectively passes mobile hydrogen in the sample. 
       FIG. 6  shows a method for reducing concentration of mobile hydrogen of metallic objects (e.g., in and/or on surfaces of the metallic objects), according to some examples of the disclosed methods. 
     As shown in  FIG. 6 , a method ( 600 ) for reducing concentration of mobile hydrogen of a metallic object can comprise: placing the metallic object into a vacuum furnace ( 602 ); drawing a vacuum in the vacuum furnace ( 604 ), as discussed above; heating the metallic object in the vacuum furnace ( 606 ), as discussed above; measuring a quantity of mobile hydrogen released from the metallic object using a hydrogen sensing device ( 608 ), once at vacuum and temperature, such measurement can be virtually instantaneous and continuous; and continuing the heating of the metallic object in the vacuum furnace until the measured quantity of mobile hydrogen released from the metallic object is below a threshold value ( 610 ). 
     As discussed above, the measuring of the quantity of mobile hydrogen released from the metallic object using a hydrogen sensing device ( 608 ) can be virtually instantaneous and continuous. The mobile hydrogen measurement is real time, effectively being measured as fast as the mobile hydrogen comes out of the metallic object. Depending on thickness of the metallic object (which impacts the time required for diffusion), the measured quantity of the mobile hydrogen released from the metallic object can be below the threshold value ( 610 ) in as little as 2 hours or as long as 24 hours. Shorter or longer times can be envisioned depending upon circumstances (e.g., problems with continuity of power, system leaks, unusual geometry of the metallic object). 
     The heating of the metallic object in the vacuum furnace can be continued as required (e.g., until the measured quantity of the mobile hydrogen released from the metallic object is below a threshold value, until the measured quantity of the mobile hydrogen released from the metallic object is reduced by a specific percentage). For example, the heating of the metallic object in the vacuum furnace can be continued until the measured quantity of the mobile hydrogen released from the metallic object is below a threshold value, where the threshold value is 1 ppm, 500 ppb, 200 ppb, 100 ppb, 50 ppb, 25 ppb, 10 ppb, or 5 ppb. For example, the heating of the metallic object in the vacuum furnace can be continued until the measured quantity of the mobile hydrogen released from the metallic object is reduced by 50%, 60%, 70%, 75%, 80%, 90%, or 100%. 
     The systems and methods of the present application should reduce mobile hydrogen from a metallic object up to 100%. In addition, the systems and methods of the present application should significantly reduce (e.g., 50%) mobile hydrogen from a metallic object in as little as two hours, with reduction in mobile hydrogen potentially approaching 100% in as little as one or two days. 
     As also shown in  FIG. 6 , after heating the metallic object in the vacuum furnace ( 606 ) and measuring a quantity of mobile hydrogen released from the metallic object using a hydrogen sensing device ( 608 ), the measured quantity of mobile hydrogen released from the metallic object is compared to a threshold value ( 610 ). If the measured quantity of mobile hydrogen released from the metallic object is below the threshold value ( 610 ; YES), then the method ends. If the measured quantity of mobile hydrogen released from the metallic object is not below the threshold value ( 610 ; NO), then the heating of the metallic object in the vacuum furnace ( 606 ) and the measuring of the quantity of mobile hydrogen released from the metallic object using the hydrogen sensing device ( 608 ) continues until the measured quantity of mobile hydrogen released from the metallic object is below the threshold value ( 610 ; YES). 
     The measuring of the quantity of mobile hydrogen released from the metallic object can comprise: drawing a sample from the vacuum furnace; and/or providing the sample to the hydrogen sensing device. 
     Drawing a sample from the vacuum furnace can comprise causing the sample to pass through an optional oxygen trap/oxygen scrubber solution subsystem and/or an optional diffusion barrier subsystem. As discussed above, the optional oxygen trap/oxygen scrubber solution subsystem reduces or eliminates oxygen gas from the sample, while the optional diffusion barrier subsystem selectively passes hydrogen in the sample. 
     Providing the sample to the hydrogen sensing device can comprise causing the sample to pass through an optional oxygen trap/oxygen scrubber solution subsystem and/or an optional diffusion barrier subsystem. As discussed above, the optional oxygen trap/oxygen scrubber solution subsystem reduces or eliminates oxygen gas from the sample, while the optional diffusion barrier subsystem selectively passes mobile hydrogen in the sample. 
     In some examples of the analytical inspection system, the metallic object can be an aerospace, automotive, defense, electronics, maritime, or rail-transport object. In some examples of the analytical inspection system, the metallic object can be an aerospace object. 
     In some examples of the analytical inspection system, the aerospace object can be an aircraft, airplane, airship, drone, glider, helicopter, hot air balloon, lifting body, missile, rocket, rotorcraft, satellite, or spaceship part. In some examples of the analytical inspection system, the aerospace object can be an airplane part, such as one or more components of a landing gear. 
     Although examples have been shown and described in this specification and figures, it would be appreciated that changes can be made to the illustrated and/or described examples without departing from their principles and spirit, the scope of which is defined by the following claims and their equivalents.