Patent Publication Number: US-2021180203-A1

Title: Vacuum impregnation of anodic oxidation coating (aoc) treated surfaces on valve metal substrates

Description:
INTRODUCTION 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     Valve metals and their alloys are increasingly used in aerospace and automotive applications because of their light weight and high strength. However, valve metals corrode under a variety of conditions, including in the presence of humid air and water. Such corrosion is exacerbated in the presence of various salts and other known corrosive agents. Even though some surface protection is afforded by forming oxide layers on valve metals by microarc oxidation (MAO) coating, the oxide layers have a high porosity, which enables humid air and/or water to infiltrate the oxide layer and contact the valve metal surface. Accordingly, methods of providing corrosion-resistance to workpieces comprising a valve metal are desired. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     In various aspects, the current technology provides a corrosion-resistant workpiece that includes a matrix comprising a valve metal or an alloy including a valve metal; an oxide layer formed on the matrix, the oxide layer including a plurality of pores, wherein each pore of the plurality has a pore volume; and a polymeric composition disposed within at least a portion of the plurality of pores, wherein greater than or equal to about 70% of the pore volume for each pore having the polymeric composition disposed therein is filled with the polymeric composition. 
     In one aspect, the valve metal is selected from the group consisting of magnesium, aluminum, titanium, zirconium, hafnium, chromium, cobalt, molybdenum, vanadium, tantalum, mixtures thereof, and alloys thereof. 
     In one aspect, the oxide layer is formed on the matrix by micro-arc oxidation. 
     In one aspect, the polymeric composition includes a polyacrylate. 
     In one aspect, the polymeric composition includes poly(acrylic acid) (PAA), poly(methacrylate) (PMA), poly(methyl methacrylate) (PMMA), poly(ethylacrylate) (PEA), poly(ethyl methacrylate) (PEMA), or combinations thereof. 
     In one aspect, the polymeric composition is disposed within greater than or equal to about 95% of the plurality of pores. 
     In one aspect, greater than or equal to about 90% of the pore volume for each pore having the polymeric composition disposed therein is filled with the polymeric composition. 
     In one aspect, the oxide layer is substantially free of vacant pores when no additional layer is disposed on the oxide layer. 
     In one aspect, the corrosion-resistant workpiece is a component of an automobile selected from the group consisting of a wheel, a pillar, a bracket, a bumper, a roof rail, a rocker rail, a rocker, a control arm, a beam, a tunnel, a step, a subframe member, a pan, a panel, or a reinforcement panel. 
     In various other aspects, the current technology provides a method of fabricating a corrosion-resistant workpiece. The method includes transferring a workpiece into a chamber at least partially filled with a monomer resin, the workpiece including a matrix comprising a valve metal or an alloy including a valve metal and an oxide layer formed on the matrix, the oxide layer including a plurality of pores, wherein each pore of the plurality has a pore volume; applying a vacuum to the chamber and removing air from the plurality of pores; releasing the vacuum and forcing the monomer resin to be disposed in at least a portion of the plurality of pores; and converting the monomer resin disposed in the at least a portion of the plurality of pores into a polymeric composition and forming the corrosion-resistant workpiece, wherein greater than or equal to about 70% of the pore volume for each pore having the polymeric composition disposed therein is filled with the polymeric composition. 
     In one aspect, each pore of the plurality has a diameter at an exposed surface of the oxide layer of greater than or equal to about 0.5 μm to less than or equal to about 20 μm. 
     In one aspect, the valve metal is selected from the group consisting of magnesium, aluminum, titanium, zirconium, hafnium, chromium, cobalt, molybdenum, vanadium, tantalum, mixtures thereof, and alloys thereof. 
     In one aspect, the applying the vacuum includes applying a vacuum pressure of greater than or equal to about 0.1 Torr to less than or equal to about 0.5 Torr for a time period of greater than or equal to about 1 minute to less than or equal to about 6 hours. 
     In one aspect, the converting the monomer resin into a polymeric composition comprises curing the monomer resin at a temperature of greater than or equal to about ambient temperature or room temperature to less than or equal to about 100° C. for a time period of greater than or equal to about 1 minute to less than or equal to about 1 hour. 
     In one aspect, the method further includes, after the converting, applying a primer layer to the workpiece. 
     In yet other aspects, the current technology provides a method of fabricating a corrosion-resistant workpiece, the method including removing air contained within a plurality of pores defined by an oxide layer having a porosity of greater than or equal to about 20% to less than or equal to about 90%, the oxide layer formed on a matrix of a workpiece, wherein the matrix includes a valve metal or an alloy including a valve metal and each pore of the plurality has a pore volume; actively forcing a monomer resin into at least a portion of the plurality of pores; and curing the monomer resin in the at least a portion of the plurality of pores to generate the corrosion-resistant workpiece, wherein greater than or equal to about 90% of the pore volume for each pore having the polymeric composition disposed therein is filled with the polymeric composition. 
     In one aspect, the removing air contained within the plurality of pores is performed by applying a vacuum to a chamber containing the workpiece and the monomer resin and the actively forcing the monomer resin into the at least a portion of the plurality of pores is performed by releasing the vacuum. 
     In one aspect, the monomer resin comprises monomers selected from the group consisting of acrylic acid, methacrylic acid, methyl methacrylic acid, ethyl acrylic acid, ethyl methacrylic acid, salts thereof, and combinations thereof. 
     In one aspect, the valve metal is selected from the group consisting of magnesium, aluminum, titanium, zirconium, hafnium, chromium, cobalt, molybdenum, vanadium, tantalum, mixtures thereof, and alloys thereof. 
     In one aspect, the oxide layer of the corrosion-resistant workpiece is substantially free of vacant pores. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1A  is a micrograph showing a porous surface of an oxide layer formed on a first magnesium matrix by micro-arc oxidation. The scale bar is 10 μm. 
         FIG. 1B  is a micrograph showing a porous surface of an oxide layer formed on a second magnesium matrix by micro-arc oxidation. The scale bar is 5 μm. 
         FIG. 2A  is a micrograph showing a cross-section of a first workpiece having a magnesium matrix, an oxide layer formed on the magnesium matrix by micro-arc oxidation, and an epoxy powder primer layer coating the oxide layer. The scale bar is 10 μm. 
         FIG. 2B  is a micrograph showing a cross-section of a second workpiece having a magnesium matrix, an oxide layer formed on the magnesium matrix by micro-arc oxidation, and a polyester primer layer coating the oxide layer. The scale bar is 10 μm. 
         FIG. 2C  is a micrograph showing a magnified portion of the micrograph of  FIG. 2B  taken at box  2 C. The scale bar is 5 μm. 
         FIG. 3A  is a schematic illustration of a workpiece comprising a matrix comprising a valve metal or an alloy of a valve metal, the matrix having a porous oxide layer formed thereon by micro-arc oxidation, wherein the workpiece is submerged in a monomer resin in accordance with various aspects of the current technology. 
         FIG. 3B  is a schematic illustration of the workpiece of  FIG. 3A  while a vacuum is applied and air is removed from the porous matrix of the workpiece and the monomer resin in accordance with various aspects of the current technology. 
         FIG. 3C  is a schematic illustration of the workpiece of  FIG. 3B  while the vacuum is removed and the monomer resin is forced into pores of the porous matrix of the workpiece in accordance with various aspects of the current technology. 
         FIG. 4A  is a schematic illustration of a workpiece comprising a porous oxide layer formed on a matrix comprising a valve metal or an alloy of a valve metal by micro-arc oxidation. The workpiece is in a state in which air is being removed from pores of the porous oxide layer in accordance with various aspects of the current technology. 
         FIG. 4B  is a schematic illustration of the workpiece shown in  FIG. 4A  in which all of the air has been removed from the pores, thus leaving the pores vacant, in accordance with various aspects of the current technology. 
         FIG. 4C  is a schematic illustration of the workpiece shown in  FIG. 4B  as a monomer resin is forced into the pores of the workpiece in accordance with various aspects of the current technology. 
         FIG. 4D  is a schematic illustration of the workpiece shown in  FIG. 4C  as a monomer resin is cured to generate a polymeric composition in the pores of the porous matrix in accordance with various aspects of the current technology. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific compositions, components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. 
     The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, elements, compositions, steps, integers, operations, 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. Although the open-ended term “comprising,” is to be understood as a non-restrictive term used to describe and claim various embodiments set forth herein, in certain aspects, the term may alternatively be understood to instead be a more limiting and restrictive term, such as “consisting of” or “consisting essentially of” Thus, for any given embodiment reciting compositions, materials, components, elements, features, integers, operations, and/or process steps, the present disclosure also specifically includes embodiments consisting of, or consisting essentially of, such recited compositions, materials, components, elements, features, integers, operations, and/or process steps. In the case of “consisting of” the alternative embodiment excludes any additional compositions, materials, components, elements, features, integers, operations, and/or process steps, while in the case of “consisting essentially of,” any additional compositions, materials, components, elements, features, integers, operations, and/or process steps that materially affect the basic and novel characteristics are excluded from such an embodiment, but any compositions, materials, components, elements, features, integers, operations, and/or process steps that do not materially affect the basic and novel characteristics can be included in the embodiment. 
     Any method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed, unless otherwise indicated. 
     When a component, element, or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other component, element, or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Although the terms first, second, third, etc. may be used herein to describe various steps, elements, components, regions, layers and/or sections, these steps, elements, components, regions, layers and/or sections should not be limited by these terms, unless otherwise indicated. These terms may be only used to distinguish one step, element, component, region, layer or section from another step, element, component, region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first step, element, component, region, layer or section discussed below could be termed a second step, element, component, region, layer or section without departing from the teachings of the example embodiments. 
     Spatially or temporally relative terms, such as “before,” “after,” “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially or temporally relative terms may be intended to encompass different orientations of the device or system in use or operation in addition to the orientation depicted in the figures. 
     Throughout this disclosure, the numerical values represent approximate measures or limits to ranges to encompass minor deviations from the given values and embodiments having about the value mentioned as well as those having exactly the value mentioned. Other than in the working examples provided at the end of the detailed description, all numerical values of parameters (e.g., of quantities or conditions) in this specification, including the appended claims, are to be understood as being modified in all instances by the term “about” whether or not “about” actually appears before the numerical value. “About” indicates that the stated numerical value allows some slight imprecision (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If the imprecision provided by “about” is not otherwise understood in the art with this ordinary meaning, then “about” as used herein indicates at least variations that may arise from ordinary methods of measuring and using such parameters. For example, “about” may comprise a variation of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in certain aspects, optionally less than or equal to 0.1%. 
     In addition, disclosure of ranges includes disclosure of all values and further divided ranges within the entire range, including endpoints and sub-ranges given for the ranges. 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     An oxide layer disposed on a workpiece formed from a matrix comprising a valve metal or an alloy comprising a valve metal, e.g., by micro-arc oxidation (MAO) inhibits corrosion to some extent relative to a corresponding workpiece that does not have the oxide layer. However, the oxide layer is porous, which allows an external environment to communicate with the underlying matrix and cause corrosion.  FIGS. 1A-1B  show micrographs of surfaces of oxide layers formed on magnesium workpieces by MAO, wherein the scale bar in  FIG. 1A  is 10 μm and the scale bar in  FIG. 1B  is 5 μm. As can be seen in these micrographs, the oxide layers have a high porosity. Air and humidity may penetrate these pores and cause corrosion at an interface between a magnesium matrix and the oxide layer. Additional coatings have been applied to oxide layers in attempts to inhibit this corrosion. For example, primers, polymers, fluoropolymers, epoxies, powder coatings, paints, clear coats, and combinations thereof have been applied to oxide layers. These coatings are applied by, for example, dipping, spraying, electrocoating, and brushing. However, these coatings are often porous themselves, which still allows the underlying matrix to communicate with the external environment and become corroded. For example,  FIG. 2A  is a micrograph showing a workpiece  10  comprising a magnesium matrix  12 , an oxide layer  14  formed on the magnesium matrix  12  by micro-arc oxidation, and an epoxy powder primer layer  16  coating the oxide layer  14  (the scale bar is 10 μm) and  FIG. 2B  is a micrograph showing a workpiece  20  comprising a magnesium matrix  22 , an oxide layer  24  formed on the magnesium matrix  22 , and a polyester primer layer  26  coating the oxide layer  24  (the scale bar is 20 μm).  FIG. 2C  is a magnified portion of the workpiece  20  of  FIG. 2B  taken from box  2 C. These micrographs illustrate the porosity of the oxide layers  14 ,  24  and show that the primer layers  16 ,  26  do not penetrate into the oxide layers  14 ,  24 . Therefore, any pores in the primer layers  16 ,  26  may allow the magnesium matrices  12 ,  22  to communicate with an environment external of the workpieces  10 ,  20 , which may cause corrosion. 
     Accordingly, the current technology provides a method of filling the pores of oxide layers to prevent, inhibit, or minimize corrosion formation by blocking communication between the underlying matrix and the external environment. Corrosion-resistant workpieces fabricated by the method are also provided. 
     More particularly, the current technology generally relates to enhanced surface coatings for workpieces comprising valve metals. As used herein, the term “valve metal” is used to refer to a metal or metal alloy that can grow nanoporous oxide films by MAO techniques. The resultant oxide layer formed on a valve metal may provide some degree of corrosion protection, as it constitutes a physical barrier between the metal and a corrosive environment. However, as discussed above, it may not provide sufficient corrosion resistance. Example valve metals that can be utilized with the present technology include magnesium, aluminum, titanium, zirconium, hafnium, chromium, cobalt, molybdenum, vanadium, tantalum, mixtures thereof, and alloys thereof. Valve metals may exhibit electrical rectifying behavior in an electrolytic cell and, under a given applied current, will sustain a higher potential when anodically charged than when cathodically charged. 
     With reference to  FIG. 3A , the current technology provides a method for fabricating a corrosion-resistant workpiece from a workpiece  30  comprising a valve metal or valve metal alloy matrix  31  (see  FIG. 4A ), i.e., a matrix comprising a valve metal or an alloy of a valve metal. The workpiece  30  can consist of the valve metal or valve metal alloy, or consist essentially of the valve metal or valve metal alloy, i.e., the matrix  31  may only also include unintended, but unavoidable impurities. The matrix  31  defines the shape of the workpiece  30 . The workpiece  30  is not limited and can be any part or object fabricated from a valve metal or from an alloy comprising a valve metal, such as a vehicle part, for example. Non-limiting examples of vehicles that have parts suitable to be produced by the current method include bicycles, automobiles, motorcycles, boats, tractors, buses, mobile homes, campers, gliders, airplanes, and tanks. In various aspects, the workpiece  30  is an automobile part selected from the group consisting of a wheel, a pillar, a bracket, a bumper, a roof rail, a rocker rail, a rocker, a control arm, a beam, a tunnel, a step, a subframe member, a pan, a panel, or a reinforcement panel. Therefore, although the workpiece  30  is shown as a pillar, it is understood that this is an exemplary aspect and that the workpiece is not in any way limited to a pillar. 
     The method comprises cleaning and desmutting the workpiece  30  and forming an oxide layer  32  on an exposed surface the matrix  31 . The oxide layer  32  can be seen in  FIGS. 4A-4D , which show an illustrated cross-sectional view of the workpiece  30  as the method is performed. The oxide layer  32  may be formed using MAO techniques to yield, e.g., a layer of magnesia or a magnesium oxide ceramic, a layer of alumina or an alumina ceramic, or a layer of titanium oxide or a titanium oxide ceramic, when the matrix  31  comprises magnesium, aluminum, and titanium, respectively, the composition of which may vary based on the electrolyte and other materials present therein. Various conventional and commercial variants of the MAO processes, including those described in U.S. Pat. Nos. 3,293,158, 5,792,335, 6,365,028, 6,896,785, and U.S. Pub. No. 2012/0031765, may be employed, each of which is incorporated herein by reference in its entirety. In one example, the MAO process may be performed using a silicate-based electrolyte that may include sodium silicate, potassium hydroxide, and potassium fluoride. The oxide layer  32  forms into the surface of the matrix  31  and away from the surface to yield an oxide layer thickness T OL  of greater than or equal to about 1 μm to less than or equal to about 60 μm, including thicknesses of about 1 μm, about 2 μm, about 3 μm, about 4 μm, about 5 μm, about 6 μm, about 7 μm, about 8 μm, about 9 μm, about 10 μm, about 15 μm, about 20 μm, about 25 μm, about 30 μm, about 35 μm, about 40 μm, about 45 μm, about 50 μm, about 55 μm, and about 60 μm (see  FIG. 4A ). As a non-limiting example, the oxide layer that forms on magnesium by MAO has a thickness of greater than or equal to about 8 μm to less than or equal to about 12 μm. 
     As can be seen in  FIGS. 4A-4D  (as well as in the micrographs of  FIGS. 1A-1B ), the oxide layer  32  comprises a plurality of pores  34 , wherein each pore  34  of the plurality has a pore volume and a diameter, i.e., a longest diameter, at an exposed surface of the oxide layer of greater than or equal to about 0.5 μm to less than or equal to about 20 μm or greater than or equal to about 0.5 μm to less than or equal to about 10 μm, including diameters of 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, or 20 μm. Accordingly, the oxide layer  32  has a porosity (i.e., a fraction of the total volume of pores over the total volume of the oxide layer  32 ) of greater than or equal to about 40% to less than or equal to about 85%, including porosities of about 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, and 85%. 
     After the oxide layer  32  is formed on the matrix  31 , the method comprises cleaning and passivating the workpiece  30  by rinsing with pH neutral deionized water. The cleaning and passivating removes particulates and electrolytes from the surface of the workpiece  30  and, thus, from the matrix  31 . 
     Referring back to  FIG. 3A , the method then comprises transferring the workpiece  30  into a chamber  36  at least partially filled with a monomer resin  38 . However, it is understood that the workpiece  30  can either be transferred into the monomer resin  38 , which is preloaded into the chamber  36 , or can be transferred into the chamber  36  and then the monomer resin  38  introduced into the chamber  36  until it completely covers the workpiece  30 . In either manner, the workpiece  30  is completely submerged in the monomer resin  38 . The interior of the chamber  36  communicates with a source of negative pressure, such as a vacuum, (not shown), by way of a port  40  and a conduit  42 . 
     The monomer resin  38  comprises monomers that are capable of polymerizing to form a polymer and a carrier. Non-limiting exemplary monomers include acrylic acid, methacrylic acid, methyl methacrylic acid, ethyl acrylic acid, ethyl methacrylic acid, salts thereof, and combinations thereof. The carrier can be any carrier that provides the below described characteristics, and can include polyglycol dimethacrylate, lauryl methacrylate, hydroxyalkyl methacrylate, surfactants, and combinations thereof as non-limiting examples. An exemplary carrier includes 60 wt. % polyglycol dimethacylate, 30 wt. % lauryl methacrylate, 5 wt. % hydroxyalkyl methacrylate, and 5 wt. % surfactant. The monomer resin  38  has characteristics that allow the monomer resin to eventually fill the pores  34  of the oxide layer  32 . These characteristics include surface tension that is less than the surface tension of water (72.8 dynes/cm at 20° C.), such as a surface tension of greater than or equal to about 28 dynes/cm to less than or equal to about 63 dynes/cm and a viscosity of greater than or equal to about 5 Cp to less than or equal to about 20 Cp. The monomers are capable of polymerizing and forming polymers such as poly(acrylic acid) (PAA), poly(methacrylate) (PMA), poly(methyl methacrylate) (PMMA), poly(ethylacrylate) (PEA), poly(ethyl methacrylate) (PEMA), and combinations thereof. 
     When the workpiece  30  is submerged in the monomer resin  38 , the pores  34  are filled with air  44  as shown in  FIG. 4A . Therefore, the method comprises removing the air  44  contained within the plurality of pores  34 . As shown in  FIG. 3B , the removal of the air  44  contained within the plurality of pores  34  (shown in  FIG. 4A ) can be performed by applying a negative pressure, i.e., a vacuum, to the interior of the chamber by way of the source of negative pressure, i.e., the conduit  42  and the port  40 . In various aspects, the negative pressure is greater than or equal to about 0.1 Torr to less than or equal to about 0.5 Torr, including pressures of about 0.1 Torr, about 0.15 Torr, about 0.2 Torr, about 0.25 Torr, about 0.3 Torr, about 0.35 Torr, about 0.4 Torr, about 0.45 Torr, and about 0.5 Torr. While the negative pressure is applied, the air  44  is removed from the pores  34  and from the monomer resin  38 , which can be seen as air pockets  46  comprising the air  44  shown in  FIG. 4A . To an observer, the air pocket  46  formation may be violent and may resemble boiling of the monomer resin  38 . As shown by the upward arrows in  FIGS. 3B and 4A , the air pockets  46  and corresponding air  44  are lifted out of both the monomer resin  38  and the plurality of pores  34  and out of the chamber  36  by way of the port  40 . The negative pressure and resulting air removal is performed for a time period greater than or equal to about 1 minute to less than or equal to about 6 hours, including times of about 1 minute, about 30 minutes, about 1 hour, about 1.5 hours, about 2 hours, about 2.5 hours, about 3 hours, about 3.5 hours, about 4 hours, about 4.5 hours, about 5 hours, about 5.5 hours, and about 6 hours, or until the air pockets  46  can no longer be seen, which is an indication that all of the air  44  has been removed from the pores  34  and the monomer resin  38 .  FIG. 4B  shows the oxide layer  32  in a state where the pores  34  are vacant, i.e., void of any gas or liquid. 
     After substantially all of the air  44  has been removed from the pores, where substantially all of the air refers to at least about 80%, at least about 85%, at least about 90%, at least about 95%, or at least about 99% of the air, the method comprises actively forcing the monomer resin  38  into the plurality of pores  34 . By “actively forcing” it is meant that a force other than gravity must be applied in order to fill the pores  34  within the monomer resin  38 . In some aspects, and as shown in  FIGS. 3C and 4C , the negative pressure is released, which causes a rush of air to enter the chamber  36  and force the monomer resin  38  downward and against the workpiece  30  so that the monomer resin  38  enters and fills the pores  34 . This air pressure is shown by the downward facing arrows in the figures. The monomer resin  38  enters at least a portion of the pores, such as greater than or equal to about 80%, greater than or equal to about 85%, or greater than or equal to about 90% of the pores  34 , or enters substantially all of the pores (greater than or equal to about 95% of the pores  34 ). Moreover, greater than or equal to about 70%, greater than or equal to about 75%, greater than or equal to about 80%, greater than or equal to about 85%, greater than or equal to about 90%, or substantially all (greater than or equal to about 95%) of the pore volume for each pore  34  having the monomer resin  38  disposed therein is filled with the monomer resin  38 . Therefore, in some aspects, substantially all of the pore volume of substantially all of the pores  34  are filled with the monomer resin  38 . 
     After the monomer resin  38  has been actively forced into the pores  34 , either the workpiece  30  is removed from the chamber  36  or the monomer resin  38  remaining in the chamber  36  is removed, such as by draining. Residual monomer resin  38  is then removed from surfaces of the workpiece  30 , such as by rinsing with a solvent (e.g., water) or by centrifuging. 
     With reference to  FIG. 4D , the method also comprises converting the monomer resin  38  disposed within the at least a portion of the pores  34  into a polymeric composition  48  and forming a corrosion-resistant workpiece  50 . In various aspects the converting is performed by curing the monomer resin  38  in the at least a portion of the plurality of pores  34  at a temperature of greater than or equal to about ambient temperature or room temperature to less than or equal to about 100° C., including temperatures of about 20° C., about 25° C., about 30° C., about 35° C., about 40° C., about 45° C., about 50° C., about 55° C., about 60° C., about 65° C., about 70° C., about 75° C., about 80° C., about 85° C., about 90° C., about 95° C., or about 100° C., for a time period of greater than or equal to about 1 minute to less than or equal to about 1 hour, including times of about 1 minute, about 5 minutes, about 10 minutes, about 15 minutes, about 20 minutes, about 25 minutes, about 30 minutes, about 35 minutes, about 40 minutes, about 45 minutes, about 50 minutes, about 55 minutes, or about 1 hour to generate the corrosion-resistant workpiece  50 . The polymeric composition  48  comprises a polymerization product of the monomer provided in the monomer resin  38 , and may comprise poly(acrylic acid) (PAA), poly(methacrylate) (PMA), poly(methyl methacrylate) (PMMA), poly(ethylacrylate) (PEA), poly(ethyl methacrylate) (PEMA), and combinations thereof, as non-limiting examples. The curing can be performed in the chamber  36 , on a countertop (e.g., when at ambient or room temperature), or in a separate oven. After the curing, greater than or equal to about 70%, greater than or equal to about 75%, greater than or equal to about 80%, greater than or equal to about 85%, greater than or equal to about 90%, or substantially all (greater than or equal to about 95%) of the pore volume for each pore  34  that had the monomer resin  38  disposed therein is filled with the polymeric composition  48 . Therefore, in some aspects, substantially all of the pore volume of substantially all of the pores  34  are filled with the polymeric composition  48 . In such aspects, the oxide layer  32  of the corrosion-resistant workpiece  50  is substantially free of vacant pores, i.e., less than or equal to about 20%, less than or equal to about 15%, less than or equal to about 10%, less than or equal to about 5%, or less than or equal to about 1% of the previously vacant pores  34  remain vacant. 
     The method then includes rinsing the corrosion-resistant workpiece  30 , either in the chamber  36  or at a different location. For example, the steps of submerging the workpiece  30  into a polymer resin, applying the negative pressure, draining, rinsing, centrifuging, heating, and rinsing can be performed in a single apparatus that includes the chamber  36 . However, it is understood that each step can also be performed in, or in association with, separate apparatuses. 
     The method optionally then comprises applying additional coatings or layers to the corrosion-resistant workpiece  50 , such as a layer comprising a primer, polymer, fluoropolymer, epoxy, powder coating, paint, dye coat, base coat, clear coat, and combinations thereof. 
     The current technology also provides the corrosion-resistant workpiece  50  made by the above method. Necessarily, the corrosion-resistant workpiece  50  comprises the matrix  31  comprising the valve metal or the alloy comprising the valve metal and the oxide layer  32  formed on the matrix  31 , the oxide layer  32  comprising the plurality of pores  34 , wherein each pore of the plurality has a pore volume. The polymeric composition  48  is disposed within the at least a portion of the plurality of pores  34 , wherein greater than or equal to about 70% of the pore volume for each pore  34  having the polymeric composition  48  disposed therein is filled with the polymeric composition  48 . 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.