Patent Publication Number: US-2020283914-A1

Title: Double coupon reference cell and methods of making same

Description:
RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 15/375,911, filed Dec. 12, 2016, which is a divisional of U.S. Pat. No. 9,550,247, issued Jan. 24, 2017, which claims the benefit of U.S. Provisional Application No. 61/847,999, filed Jul. 18, 2013, the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a cathodic protection device that allows for corrosion testing of a system, more particularly, to such a device having dual coupon references to provide accurate measurement of the corrosive nature of a particular environment. 
     BACKGROUND 
     Cathodic protection systems are generally in use for corrosion protection of metal structures. Many current cathodic protection devices employ the use of corrosion coupons in order to measure conditions of a particular system, more specifically the corrosivity of tanks and various types of operating equipment. However, these devices are subject to a number of drawbacks, many of which affect the most important objective of the device: providing an accurate measurement of the corrosive nature of a particular environment with respect to a specific type of material. 
     Various factors relating to both corrosion coupons and cathodic protection devices are relevant in measuring the corrosive nature of a particular environment. With regards to coupons, it is necessary that they are placed in a representative location within the system being monitored such that the location is representative in temperature, pressure, water chemistry, chemical additions, bacterial populations, and solids loading. It is also important that the coupon be electrically isolated from both the cathodic protection device and the system to be monitored in order to prevent galvanic effects that could potentially influence the coupon reading. 
     The necessary calculation that leads to the measurement of the corrosion rate is based upon the surface area of the coupon. Currently, many of the corrosion coupons in use are in the form of rings, as disclosed in U.S. Pat. No. 4,208,264 (Polak), and thus result in poor surface area for control of the calculation leading to the measurement of corrosion. Therefore, it is advantageous to provide a coupon with adequate exposure of surface area for control of this specific calculation. 
     In order to expose the coupon to the particular environment measured, it is necessary for coupon placement to be on the outside of the housing unit, which contains the reference cell. Means of placing or mounting the coupons on the housing unit have generally included the use of metallic nuts and/or bolts as fasteners, as disclosed in U.S. Pat. No. 4,928,760 (Freitas). In addition to using nuts and bolts for fastening the coupons to the device, nuts and bolts are also used in fastening wiring and leads to the coupons. Issues arise, however, when the metallic nuts and bolts begin to corrode themselves. Not only is the life of the device decreased, but the corrosion of the nuts and/or bolts begins to interfere with the readings taken by the coupon to calculate the corrosion measurements. Therefore, alternative means to fasten various components of the device are desirable. 
     Further, the reference cell housing portion of many prior art devices consists of a porous ceramic vessel, an example of which is disclosed in U.S. Pat. No. 4,208,264 (Polak). The porous nature of the ceramic vessel, accompanied with exposure to the outside environment, allows for water from the outside environment to flow through the vessel and into the housing unit. It also allows for penetration of conductive material contained within the housing unit, thus resulting in loss of conductive material to the outside environment. Leakage into the vessel also results when the coupons are not properly sealed within the coupon jacket. Existing methods of sealing the coupon within its housing component result in gaps around the outside of the coupon, thus allowing for water from the outside environment to enter causing further corrosion to the coupon. Therefore, a method of improving the sealing of the coupon within its housing is needed. 
     Overall, there has not been available to date any device that provides the improvements necessary for providing accurate exposure of coupon surface area, reducing metal galvanic corrosion, eliminating loss of conductive material from within the housing of the device, and sealing and preventing leaks from the housing of the device. 
     SUMMARY 
     In one aspect cathodic protection devices are disclosed that include dual coupons constructed to improve the accuracy and reproducibility of measurements of the corrosive nature of a particular environment with respect to a specific type of material. Herein, the coupons included in the cathodic protection device are disc-shaped and provide improved accurate exposure of a known surface area to the outside environment. In one embodiment, the cathodic protection devices include a housing enclosing a reference cell and a conductive media, dual coupons on the exterior of the housing, and a hydrophilic porous member disposed in the housing with one surface thereon in communication with the conductive media and another surface exposed to a surrounding environment to provide measurements of the corrosive nature of the surrounding environment. The cathodic protection devices include the improvement of a disc-shaped coupon within a coupon jack that has a generally patch-sized body that includes a groove recessed into a surface thereof, and a wire lead directly attached to the disc-shaped coupon. The wire lead is sealed within the groove of the coupon jacket with a material that forms a watertight seal, which may also be an electrical insulator. In one embodiment, the material is an electrically insulating material as well as forming the watertight seal. The material may be an epoxy, a plastic, an epoxy-plastic, or combinations thereof. 
     In another improved embodiment the cathodic protection devices include some or all of the features described above and the improvement of a hydrophilic porous member. The hydrophilicity of the porous member draws a sufficient amount of moisture therein and the presence of this moisture prevents water from the outside environment from being able to flow through the porous member and into the housing, in particular into the conductive media, and also prevents conductive media within the housing unit from flowing out and into the surrounding environment. The hydrophilic porous member is typically less porous than the porous ceramic materials used in the prior art, thus affording the desired objective of preventing the penetration of conductive material contained within the housing unit from flowing out and into the outside environment. 
     In another aspect, methods of assembling the coupon jacket assembly are disclosed. The coupon jacket assembly is formed by providing one or more blanks of discrete patch-sized units having a groove in a surface thereof, placing the one or more blanks onto a jig having a tongue shaped to fit within the groove, heating the blanks to a sufficient temperature to mold them into a preferred contour, and pressing a mold onto the blanks to impart the preferred contour to the blanks, referred to now as molded blanks. Thereafter, a pocket for holding a disc-shaped coupon is formed in the molded blanks. The pocket includes an aperture connecting the pocket to the groove. Next, the disc-shaped coupon with a wire lead attached thereto has the wire lead threaded through the pocket, an epoxy-plastic welder applied to the inside surface of the pocket and, optionally to the disc-shaped coupon, and is pressed into the pocket of the coupon jacket with the disc-shaped coupon seated in the pocket and the wire lead lying in the groove. The groove is thereafter filled with material for forming a watertight seal and the coupon assembly is mounted to the housing which will house a reference cell and a conductive media. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a photograph of a prior art cathodic protection device having dual coupon references that are each an annular, cylindrical, metallic ring. 
         FIG. 2  is a top plan view of one embodiment of an improved cathodic protection device having dual coupon references. 
         FIG. 3  is an exploded perspective view of the embodiment of  FIG. 2 . 
         FIGS. 4A-4D  are perspective views of one embodiment of a method of forming a coupon jacket for the embodiment of  FIG. 2 . 
         FIG. 5  is a perspective view of one embodiment of a coupon-wire assembly. 
         FIG. 6  is a perspective view that illustrates the manner in which the coupon-wire assembly of  FIG. 5  is threaded through the aperture in the coupon jacket of  FIG. 4D  after a pocket and aperture are formed therein. 
         FIG. 7  is a perspective view of the top side of the coupon jacket assembly formed from the method depicted in  FIG. 6 . 
         FIG. 8  is a perspective view of the underside of the coupon jacket assembly formed from the method depicted in  FIG. 6  prior to filling the cavity. 
         FIG. 9  is a perspective view of the underside of the coupon jacket assembly formed by the method depicted in  FIG. 6  after the cavity has been filled. 
         FIGS. 10A and 10B  are a perspective top side view and a perspective bottom side view, respectively, of an alternate embodiment of a coupon jacket. 
         FIG. 11  is a perspective view of inserting a porous member into an end cap. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description will illustrate the general principles of the invention, examples of which are additionally illustrated in the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. 
     In the past, there have been attempts to measure the conditions of an environment and the corrosivity of tanks and various types of operating equipment through the use of coupon references located on the exterior of an elongate housing of a cathodic protection device, such as shown in the photograph of  FIG. 1 . However, these cathodic protection devices fail to accurately measure the corrosive nature of the outside environment because the measurements are impacted by flaws in the cathodic protection device itself. Annular coupons or long, narrow coupons have been employed in prior art devices, which result in inaccurate surface area exposure because of gaps between the housing surrounding the coupon and the coupon itself. The gap allows water or other fluid to leak within the housing and a larger surface area is exposed than intended. Additionally, the wire lead is connected by threading directly to the annular coupon, which provides a connection that is highly susceptible to corrosion. These cathodic protection devices fail to provide complete isolation of the coupon connection, which contributes to the inaccuracy of the coupon readings. 
       FIG. 1  illustrates one embodiment of a partially disassembled prior art cathodic protection device having dual coupon references, generally designated  100 , that suffers from the defects described above. The prior art cathodic protection device  100  includes the following components to provide measurements of the corrosive nature of a particular environment: a housing  102  enclosing a reference cell and conductive material and sealed by end caps  104 , one of which includes a ceramic plug  106 , and having two coupon housings  108  that each enclose a cylindrical coupon reference  110  seated around a portion of the housing  102  (only one of which is shown because the photograph is of a partially disassembled device). This particular embodiment employs the use of screws to attach a wire lead to each cylindrical coupon reference  110  as described above. Further, each cylindrical coupon  110  is not securely contained within the coupon housing components  108  and as such, a gap  111  is created between the coupon housing component  108  and an outside edge of the cylindrical coupon  110 . Undesirably, this gap  111  allows water and other fluids to leak into the housing  108 . The ceramic plug  106  is made of a highly porous ceramic material, which results in the leakage of conductive material contained within the housing  102  into the outside environment, which is undesirable. Further, the porosity of the ceramic plug  106  allows for water from the outside environment to flow into the elongate housing  118 , which is also undesirable. The end caps  104  are meant to seal the housing unit from leaks, however the end caps  104  of this embodiment  100  fail to adequately do so. In particular, the end cap opposite the ceramic plug  106  is glued on in the field after the conductive material and reference cell are placed in the housing  102 . The glue provides an inadequate seal thereby reducing the active life of the device. 
     Now referring to  FIGS. 2 and 3 , one embodiment of the improved cathodic protection device, generally designated by reference number  112 , more accurately measures the conditions of an environment through the use of dual disc-shaped coupons  142  within coupon jackets  132  (or  132 ′ in  FIGS. 10A and 10B ) mounted on the exterior of the elongate housing  118 . The improved cathodic protection device  112  overcomes the deficiencies in the prior art described above. 
     The elongate housing  118  may be made of a dielectric material, such as PVC (but is not limited thereto), and may be a cylindrical tube (but is not limited thereto). The housing unit  118  has a first end  122  and a second end  123 . The first end  122  includes a first female adaptor  124  and the second end  123  includes a second female adaptor  126 . After the housing unit  118  is filled with a reference electrode  129 , shown in  FIG. 3 , and a conductive media (not shown), the housing is sealed by inserting a first end cap  125  into the first female adaptor  124  and a second end cap  131  into the second female adaptor  126 . The first end cap  125  includes a bore having a hydrophilic porous member  154  therein, which is more clearly seen in  FIG. 11 . The second end cap  131  includes a bore  136  therethrough and has a wire or cable  130 , from the reference cell  129 , extending through the bore. The wire  130  may include a cord grip  128  that is also received in the bore of the second end cap  131  to seal the wire  130  thereto with a watertight seal. While the embodiment in  FIGS. 2 and 3  is shown to include female adaptors  124 ,  126 , these are not required. Instead, the elongate housing  118  may have an integral first end  122  and second end  123  that each form a connector or a seat for receipt of the end caps  125 ,  131 . 
     In one embodiment, the first end cap  125  and the second end cap  131  are both threaded and the first female adaptor  124  and the second female adaptor  126  are threaded such that the first and second end caps are connected by threading to the respective first and second female adaptors  124 ,  126 . This type of connection is beneficial since it is easy to assemble and it provides a watertight seal that is better than the seal in the prior art device shown in  FIG. 1 . The seal may also be enhanced by the addition of a water sealant tape or chemical substances applied to the threads. In another embodiment, the opposite configuration is possible, i.e., the female adaptors  124 ,  126  may be threaded into their respective end caps  125 ,  131 . 
     The hydrophilic porous member  154  may be or include a ceramic material having a flow rate of about 0.5 ml/hr/cm 2  to about 180 ml/hr/cm 2  at about 1 atm of pressure. In operation, the hydrophilic porous member draws in moisture and holds it therein, which prevents the conductive media housed within the elongate housing  118  from seeping through the hydrophilic porous member. Additionally, excess moisture from the surrounding environment is prevented from seeping into the housing and into the conductive media. The hydrophilic porous member  154  provides the cathodic protection device  112  with the added advantage that it can be buried vertically in the ground (with the reference cell directed upward toward the surface of the ground and sky or downward opposite thereof) with no worry of leakage of the conductive material therefrom or the seepage of water from the environment into the elongate housing  118 . In one embodiment, the hydrophilic porous member  154  is a disc of porous ceramic, such as the ceramic material described above. 
     Still referring to  FIGS. 2 and 3 , but also to  FIGS. 5-9 , the coupon jackets  132  each contain a disc-shaped coupon  142  and are preferably mounted on the exterior surface of the elongate housing  118  oriented 180° apart from one another. Similarly, the coupon jacket  132 ′ in  FIGS. 10A and 10B  can contain a disc-shaped coupon  142  and be mounted on an exterior surface of the elongate housing  118 . Each disc-shaped coupon  142  has a primary surface  143  exposed to the surrounding environment. By referring to the coupon as disc-shaped, there is no intention to limit this to a circular shape even though a circular shape is illustrated in the drawings. The disc-shaped coupon may be an oval, trapezoid, diamond, octagon, etc. 
     With reference to  FIGS. 6-9 , each coupon jacket  132 ,  132 ′ is a generally patch-sized body  133  having a groove  138  in a surface thereof and a pocket  150  recessed into the opposite surface thereof. A patch-sized body is one that is generally small relative to the overall outer surface area of the elongate housing  118  and does not cover a portion of the surface area that extends completely around a transverse cross-sectional portion thereof. For instance, when the housing is a cylindrical shape, the patch-sized body  133  is not a ring about the housing. An aperture  151  connects the pocket  150  to the groove  138 . During the methods of making the coupon jackets  132 ,  132 ′, discussed below, a shape is imparted to the underside  144  (best seen in  FIGS. 8-9 and 10B ) thereof so that the underside  144  of the coupon jackets  132 ,  132 ′ conforms to the exterior surface of the housing  118 , in particular to the contour thereof. In the embodiment illustrated in the drawings, the housing  118  has a cylindrical exterior surface and the underside of the coupon jacket  132  and coupon jacket  132 ′ is an arc that can seat thereon. Each coupon jacket may also include one or more mounting holes  140  extending through the patch-sized body  133 , as seen in  FIGS. 2-3 and 6-9 . 
       FIGS. 4A-D  illustrate one method of forming the coupon jackets  132  of  FIGS. 6-9  to provide the coupon jackets with a contour that matches an exterior surface of the housing  118 . As seen in  FIG. 4A , a plurality of blanks  127  are provided that may already include mounting holes  140  and are placed on jig  134  (also referred to herein as a mandrel fixture). The mandrel fixture  134  includes a tongue  135  and the blanks include a groove  138  that mates with the tongue  135 . After the blanks  127  are attached thereto, the mandrel fixture  134  is placed into an oven, which may have been preheated, at a temperature for a period of time selected to soften the blanks  127  so that they are moldable to the contour/shape of the jig  134 . In one embodiment, when the blanks are PVC, the blanks  127  (on the jig  134 ) are placed in an oven having a temperature of about 200° F. for about 30 minutes. Thereafter, as seen in  FIGS. 4B and 4C , a forming tool  139  is placed on top of the blanks  127 , while the blanks are still hot, and is pressed down thereon and held in that position, for example by clamps. The attached forming tool  139  is left on the blanks  127  during cooling, for example to room temperature. Thereafter, the forming tool  139  is removed,  FIG. 4D , and the molded blanks  127 ′ are removed from the jig  134 . 
     In the embodiment of  FIGS. 4A-D , the forming tool  139  provides a mold for a curved structure to enable formation of coupon jackets  132  that can be seated on the cylindrical housing  118 . Then, the molded blanks  127 ′ are processed to form the pocket  150  for the disc-shaped coupon  142  and the aperture  151  within the pocket  150  as shown in  FIG. 6 . The pocket  150  and aperture  151  may be machined into the piece. Additionally, the portion of the molded blank  127 ′ that receives the pocket  150  may also be planed to have a planar surface  154  before or after the pocket and aperture are formed therein. 
     In another embodiment, the coupon jacket may alternately be made by cutting a patch-sized component from a stock material and machining the pocket  150 , the aperture  151 , and the groove  138  therein simultaneously or sequentially. Machining is intended herein to encompass, cutting, etching, drilling, etc. The method also includes shaping the underside  144  to a shape that conforms to an exterior surface of the elongate body  118 . For example, the coupon jacket  132 ′ in  FIGS. 10A and 10B  may be cut from a cylindrical rod of stock material and the pocket  150  aperture  151 , groove  138 , and underside  144  may be machined therein. 
     A coupon-wire assembly  146  is illustrated in  FIG. 5 . The coupon-wire assembly  146  includes the disc-shaped coupon  142  having a coupon wire lead  120  directly connected thereto. The coupon wire lead  120  contains a wire  148  soldered or brazed to the back surface  145  of the disc-shaped coupon  142 . This is beneficial because it eliminates the use of a screw to connect a wire to the coupon material, which if present is a known point of failure because it is susceptible to corrosion. 
       FIG. 6  illustrates the pocket  150  and aperture  151  of the coupon jacket  132  described above, which enables the insertion of the coupon-wire assembly  146  into the coupon jacket  132  so that the disc-shaped coupon  142  can be seated in the pocket  150  as seen in  FIG. 7 . The wire lead  120 , once attached to the disc-shaped coupon  142 , is threaded through the pocket  150  and through the aperture  151 , and once through, the disc-shaped coupon  142  is pressed into the pocket  150  thereby placing the wire lead  120  into the groove  138  of the coupon jacket. The disc-shaped coupon  142  may be coated with glass tape prior to assembly within the coupon jacket  132 . The back side  145  of the disc-shaped coupon  142  is coated with a material for forming a watertight seal and also acts as an insulator. The material may be an epoxy, a plastic, an epoxy-plastic, any other suitable insulating material, and combinations thereof. The surface(s) of the pocket  150  may also be coated with the material for forming the watertight seal. 
       FIG. 7  illustrates the coupon-wire assembly  146  assembled within the coupon jacket component  132 . The disc-shaped coupon  142  is pressed into the pocket  150  in the coupon jacket unit  132  and any excess material for forming a watertight seal is wiped away and/or pressed down into the gap  153  around the edge of the coupon. A sufficient time is allotted for the material for forming a watertight seal to set or cure. In one embodiment about 30 minutes was allotted. 
     Thereafter the coupon jacket is turned so that the underside  144  is facing upward and the groove  138  is filled with a material for forming a watertight seal.  FIG. 8  illustrates the underside  144  of the coupon jacket unit  132  before the material for forming a watertight seal is placed in the groove  138 , and  FIG. 9  is an illustration of after. As seen in  FIG. 8  the wire lead  120  lies in the groove  138 , and  FIG. 9  shows that the wire lead  120  and wire  148  within the groove  138  is completely encapsulated by the material for forming a watertight seal. The material that forms the watertight seal is also an electric insulator, as discussed above. The material for forming a watertight seal used to fill the groove  138  should be added in an amount large enough to allow the aperture  151  of the pocket  150  to be overfilled so that the exterior can be wiped and provide a smooth underside  144 . Again, sufficient time is allotted for the material for forming the watertight seal to set or cure. In one embodiment, about an hour was allotted. This coupon jacket assembly may be attached to a mandrel, such as a PVC pipe, and wrapped with a layer of double sided glass tape prior to the setting or curing phase. Once cured, the glass tape that was originally placed over the exposed surface  143  of the disc-shaped coupon  142  is removed. 
     Once the coupon-wire assembly  146  is mounted to the exterior surface of the elongate housing  118 , the wire  148  can be wound and secured to the housing until the housing is filled with the conductive media (not shown) and reference cell  129 . Once the housing is fully assembled as shown in  FIG. 1 , the wires  148  from both coupon-wire assemblies  146  are run along the outside of the elongate housing  118  and then along the reference cell wire  130 . The wires  148  may be secured by tape, adhesive, clips, latches, cable ties and/or zip-ties to the elongate housing  118  and/or the reference cell wire  130 . Accordingly, there are three separate wires for connection of the cathodic protection device  112  to a junction box and thereafter connected to an appropriate component in a system being monitored and to a monitoring station having a datalogger, a computer, a network connection, or the like. As mentioned above, the cathodic protection device is intended to be buried underground. Typically, the device is buried at a location that places at least one of the coupon-wire assemblies  146  generally close to the object to be protected, such as a pipeline or tank. In one embodiment, at least one of the coupon-wire assemblies  146  is approximately six inches from the pipeline or tank, which places the coupon  142  in about the same electrolytic, external environment as the pipeline or tank. Although it is not absolutely necessary, it is considered desirable to place the coupons  142  relatively close to the pipeline or tank to achieve the most accurate measurements. 
     The coupon  142  is preferably made of the same type of metal as the pipeline or tank for the most accurate results. However, the coupon  142  need only be made of a similar metal material as the pipeline or tank, and thus need not be the exact material to achieve accurate measurements. The coupon  142  is typically not coated with the same protective coating applied to the surface of the pipeline or tank. Due to the electrical conduction through the coupon wire  120 , at least one of the coupons  142  is electrically connected to the pipeline or tank. In this manner, the coupon  142  is exposed to the same external environment and receives about the same level of cathodic protection currents as the pipeline or tank. 
     Referring now to  FIG. 11 , an exploded view of the hydrophilic porous member  154  and the first end cap  125  is provided. The hydrophilic porous member  154  has an exposed surface  159  facing upward away from the first end cap  125 . This exposed surface  159  is masked with a layer of glass tape, which may be a single sided glass tape. Then, a bead of material for forming a watertight seal is applied to the seat  156  within the bore  162  of the first end cap  125 . The outer edge  158  of the hydrophilic porous member  154  is covered with material for forming the watertight seal and is pressed into the bore  162  onto the seat  156  so that the material for forming the watertight seal fills any space between the hydrophilic porous member  154  and the bore  162 . Thereafter the glass tape mask is removed from the exposed surface  159  of the hydrophilic porous member  154 .