Improving Surface Characterics In Nickle Alloys Rev May 08 Inc Passivation


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Explanation of Electropolishing and the benefits received

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  • The standard or typical treatment includes the items listed, including: An initial DI water rinse; a derouging phase, if required; a cleaning or decontamination phase with detergents; a passivation phase; a sanitization or oxidation phase and final rinse to a conductivity endpoint. During the passivation phase, the amount of iron dissolved into the solution is measured. This is our means to verify passivation endpoint is met; All iron has been dissolved from the surface. The conductivity endpoint is verifying the final rinse to show that the effluent water quality matches the influent water quality; or water coming out the system is as clean as the water going in.
  • Here is the reason passivation is required for newly fabricated or constructed systems. This is a series of Auger analyses that were performed across the weld area of a 316L tube sample. It shows that the area at and near the weld bead is very high in iron with almost no chromium at the surface, yet still in an oxidized condition. The heat effected zone appears on both sides of the weld, with relatively speaking, equal parts iron and chromium. However, this associates with a dark band that consists of chromium carbide precipitation and an equally susceptible area for corrosion. That is why you often see iron oxide rouge on the weld or in the heat effected zone from corrosion. Now, if you passivate this weld…..
  • We can repair the damage due to welding with passivation and re-form the passive layer to form a 2 to 1 chromium to iron ratio protective film. You see that the weld area and the heat effected zone has been fixed. These areas are now as good as the standard tubing area ON THE SURFACE . One note : If you have weld damage below the three or four molecular levels, it will still show through, visibly; and you will likely, with some amount of corrosion, break through the protective passive layer and get to the damage zone below over time. The corrosion rate will be much higher than expected, even for the alloy, resulting in pitting corrosion and possible tube failure.
  • Improving Surface Characterics In Nickle Alloys Rev May 08 Inc Passivation

    1. 1. Improving Surface Characteristics in Nickel Alloys through Electropolishing Ken Kimbrel This presentation is the intellectual property of UltraClean Electropolish, Inc. Do not reproduce in part or in whole without prior written authorization of UltraClean Electropolish, Inc. 03-01-06
    2. 2. Electropolishing Why Bother? Electropolishing Why Bother?
    3. 3. Do You Think This Surface is Easier to Clean or….. 20Ra
    4. 4. Would This Surface Be Better? 20Ra
    5. 5. 10 Ra – 2B Sheet Metal 1000 X 2B Sheet Metal 10Ra, 1500X How About This vs. …..
    6. 6. 5Ra – 2B Electropolish 2B – Electropolished 7Ra, 1500X This?
    7. 7. ELECTROPOLISH The Ultimate Product Contact Surface! <ul><li>Electropolishing provides optimum micro-surface finish! </li></ul><ul><li>Electropolishing provides the minimum total surface area! </li></ul><ul><li>Electropolishing provides pure alloy without contamination or damage at the materials surface (product contact interface) </li></ul>
    8. 8. ELECTROPOLISH The Cleanest Surface Possible <ul><li>Electropolished alloy surfaces offer optimum cleanability! </li></ul><ul><li>Electropolished alloy surfaces offer optimum sterility! </li></ul><ul><li>Electropolished surface offers optimum resistance to corrosion for any given alloy! </li></ul><ul><li>Electropolished surface offers rouge formation reduction when base material is the cause! </li></ul>
    9. 9. Vocabulary <ul><li>Electropolish: the electrolytic removal of metal in a highly ionic solution by means of electrical potential and current. </li></ul><ul><li>Anode: the work piece, part, or component connected to the positive side of a DC power source that becomes a sacrificial anode when the part is exposed to the electropolish process </li></ul><ul><li>Cathode: the necessary conductor that is connected to the negative side of a DC power source and is present in the circuit during the electropolishing process </li></ul><ul><li>Electrolyte: An acid blend into which the work piece is placed for processing. The bath is the ionic solution which wets the work piece and carries the metal ions from anode to cathode. </li></ul>
    10. 10. Vocabulary <ul><li>Spot EP: the practice of localized electropolishing whereby the surface of the work piece is exposed to the electropolishing process for an adequate amount of time and at a sufficient current density to produce a qualified electropolished finish as described in the BPE Specification for Electropolishing (a.k.a. “in situ”, “brush”, “hand tool” electropolishing). </li></ul><ul><li>Buffing: a practice of mechanical polishing using a polishing compound made up of an abrasive in a grease bonding material that is applied to the surface with polishing wheels made of cotton, hemp, felt, etc. The buffing wheel is “loaded” with compound then the wheel is pressed onto the surface while spinning at a high RPM, producing a very fine directional grain on the surface making the surface bright and reflective. </li></ul>
    11. 11. Electropolishing; How it Works <ul><li>A surface to be electropolished is made anodic (+) in a DC power circuit </li></ul><ul><li>The work is then exposed to an acid electrolyte (dipped or wetted) </li></ul><ul><li>A cathode (-) is present adjacent to the portion of the work that requires electropolishing </li></ul>
    12. 12. Electropolishing; How it Works
    13. 13. Electropolishing; How it Works
    14. 14. Electropolishing – How it Works <ul><li>Generally electropolishing takes place at the manufacturing facility, or in a stand alone job shop that offers the service to equipment manufacturers. </li></ul><ul><li>Vessel Photo Courtesy NORTHLAND STAINLESS, INC. </li></ul>
    15. 15. Electropolishing; How it Works
    16. 16. Electropolishing – How it Works The process can also be performed “on site” or “in situ” by firms that specialize in this service. This allows equipment purchased without the finish, or equipment originally electropolished and damaged, to be repaired or completely electropolished where it sits. Electropolishing; How it Works
    17. 17. Electropolishing; How it Works 120 Ra MILL FINISH - Hot Rolled Annealed 316 Plate Material
    18. 18. Electropolishing; How it Works 35 Ra ELECTROPOLISHED - Hot Rolled Annealed 316 Plate Material
    19. 19. Electropolishing; How it Works As Electropolishing Exposure Increases Microscopic Smoothing Continues Until Optimum Improvement is Achieved
    20. 20. Electropolishing; How it Works <ul><li>When the power is applied an anodic film forms on the surface of the work and the material begins to be removed ion by ion </li></ul><ul><li>The effect on the microscopic surface is to smooth and level as the microscopic “peaks” dissolve more rapidly than the microscopic “valleys” due to the increase in resistance to current flow as the film get thicker in the valleys </li></ul>
    21. 21. Electropolishing; How it Works When the process is allowed to continue for an adequate amount of time the surface becomes microscopically smooth and virtually featureless As the anodic film becomes uniform in thickness the benefits of electropolishing have been accomplished and material will continue to be removed uniformly until the process is stopped
    22. 22. Electropolishing; Why it Works <ul><li>The microscopic “featureless” surface leaves little or no grain boundaries, or surface imperfections, dramatically reducing sites for corrosion to start </li></ul>2B 304 Sheet Metal Electropolished
    23. 23. Optimized Micro Surface & Surface Area Reduction <ul><li>Electropolishing offers a microscopic featureless surface. </li></ul><ul><li>Electropolishing offers a total surface area that has been dramatically reduced. </li></ul>
    24. 24. 2B Stainless Sheet Metal SEM 1500X – 304 Stainless Steel Note the cross section in the following slide to see illustration of surface roughness
    25. 25. 2B Stainless Sheet Metal White Light Interfermetric Surface Analysis Observe this cross section Ra 7.4uin
    26. 26. #4 Stainless Sheet Metal SEM 1500X – 180 grit 304 Stainless Steel
    27. 27. #4 Stainless Sheet Metal Ra 11.5uin
    28. 28. Electropolished Stainless Coupon SEM 1500X - 304 Stainless Steel
    29. 29. Electropolished Stainless Sheet Metal Compare this to previous slides Ra 2.3uin
    30. 30. Ra – How Important Is It? “ Ra is the most important thing to me “ (famous engineer) <ul><li>20 Ra mech. Polish 20 Ra Electropolished </li></ul>Both surfaces shown here measure 20Ra. Which surface is best for high purity applications?
    31. 31.
    32. 32. Electropolishing; Why it Works Electropolishing allows for the removal of any distorted or “damaged” material layer that will be present following grinding, sanding, or machining. #4, 3A, 180 grit 304 sheet Electropolished
    33. 33. Mechanical Polishing/Sanding/Grinding to achieve a specific Ra will cause a damaged layer and/or heat effected zone to be produced. <ul><li>This damaged layer will include material smeared over impurities such as: </li></ul><ul><ul><li>Abrasive material/compounds </li></ul></ul><ul><ul><li>Iron or other contamination from handling/forming equipment </li></ul></ul><ul><ul><li>Paint, dye, grease, adhesives </li></ul></ul><ul><li>Mechanical finishing operations all cause damage to the material for some depth below the surface. The depth of this damage will vary depending on how aggressively the material was worked. </li></ul>
    34. 34. J. Wulff illustrates this damage on honed, ground, and electropolished samples of 18-8 CrNi. <ul><li>7. Oxide (0-5µm) </li></ul><ul><li>6. Deformed Oxide with Grit Inclusions (5-18µm) </li></ul><ul><li>5. Deformed Austenite (18-22µm) </li></ul><ul><li>4. Cold Deformed Ferrite and Deformed Austenite (22-25µm) </li></ul><ul><li>3. Cold Deformed Ferrite (25-29µm) </li></ul><ul><li>2. Austenite and Cold Deformed Ferrite (29-34µm) = (.00134”) </li></ul><ul><li>1. Austenite only </li></ul>On the honed sample a layer of “Austenite and Cold Deformed Ferrite” sits atop of a layer of “Cold Deformed Ferrite” to a depth of 5 µm (.00002”). The ground sample had seven distinct layers of non-austenite material atop the pure stainless. The seven layers top to bottom; HONED GROUND E-POLISH HONED GROUND E-POLISH .001”
    35. 35. Damaged Layer – “Bielby Layer” 180 grit sanded surface 180 Grit -Electropolished .0003”
    36. 36. Damaged Layer – “Bielby Layer” 80 grit sanded mill plate – damage .0006”
    37. 37. The Bielby Layer <ul><li>Mechanical finishing is performed to achieve required Ra on metal </li></ul><ul><li>surfaces will result in crystal fractures and other structural changes. </li></ul><ul><li>Oxides, polishing compounds, and other materials become </li></ul><ul><li>embedded in the distorted crystal structure. </li></ul><ul><li>These conditions allow the formation of surface corrosion </li></ul><ul><li>cells. </li></ul><ul><li>This condition is known as the Bielby layer. </li></ul><ul><li>Complete electropolishing will completely remove this damaged layer and all entrapped materials providing a clean pure alloy surface. </li></ul>
    38. 38. Bacterial Control NO ELECTROPOLISH ELECTROPOLISHED The Cold Worked, Damaged, or Beibly layer offers significant site for bacterial adhesion and bio-film formation. Bacterial bio-films can contribute to corrosion as they can breakdown the passive film underlying the formations. If the bio-film is them successfully removed an “active site” (non-passivated) can allow corrosion to initiate via a galvanic effect.
    39. 39. “ Multiple imaging techniques demonstrate the manipulation of surface to reduce bacterial contamination and corrosion” J.W. Arnold, D.H. Booth, O. Suzuki, & G. W. Bailey – Journal Of Microscopy, Vol. 216, Pt 3 Dec. 2004 In this study the researchers exposed samples of 2B “mill finish” (control) and the same material electropolished. Four sets of disc were included in this study; A 2B “mill finish” B Electropolished C 2B followed by corrosive treatment D Electropolished followed by corrosive treatment Corrosive Treatment: “The disks were placed in 100ml purified water, autoclaved for 1h, brought to room temperature and water supplemented to 100ml…repeated 50 times and the process carried out twice per day”
    40. 40. “ Multiple imaging techniques demonstrate the manipulation of surface to reduce bacterial contamination and corrosion” J.W. Arnold, D.H. Booth, O. Suzuki, & G. W. Bailey – Journal Of Microscopy, Vol. 216, Pt 3 Dec. 2004
    41. 41. Bacterial Control <ul><li>“ Bugs like to hide and form colonies” </li></ul>From: Edstrom Industries, Inc. (Update7)
    42. 42. Bacterial Control <ul><li>“ Electropolishing eliminates the hideouts” </li></ul>From: Edstrom Industries, Inc. (Update7)
    43. 43. Material Applications & Benefits <ul><li> Some of the materials routinely being electropolished; </li></ul><ul><li>Aluminum </li></ul><ul><li>AL-6XN </li></ul><ul><li>Copper Alloys </li></ul><ul><li>Copper-Nickel </li></ul><ul><li>C22, C276 Hastelloy </li></ul><ul><li>600, 718, X750, 800 Inconel </li></ul><ul><li>Incoloy </li></ul><ul><li>Permalloy </li></ul><ul><li>200, 205, 220, 270 Nickel </li></ul><ul><li>400, K-500 Monel </li></ul><ul><li>200-300-400 Stainless Steels </li></ul>Many Materials Can Benefit From Electropolishing
    44. 44. Material Applications & Benefits AL-6XN As Received 1000X
    45. 45. Material Applications & Benefits
    46. 46. Material Applications & Benefits AL-6XN Mechanical Polished 1000X
    47. 47. Material Applications & Benefits
    48. 48. Material Applications & Benefits AL6XN Electropolished 1000X
    49. 49. Material Applications & Benefits
    50. 50. Material Applications & Benefits <ul><li>In the most critical applications using 316L stainless steel bar stock, special batches have been formulated to insure the best possible finish following electropolishing . </li></ul>Chart & Photomicrographs – Pall Corporation, “Selection of 316 L (SS) for High Purity Semi-conductor Gas Filter Assemblies”
    51. 51. Electropolishing VS. Buffing <ul><li>Although similar in appearance; buffing should never be allowed to be the final surface finish on product contact surfaces. </li></ul>Embedded aluminum- oxide abrasive residue Buffed Electropolished
    52. 52. “ Buffing Looks Good” <ul><li>Buffing is often used to make a component look bright and mirror like. Unfortunately this practice is often provided for cosmetic reasons on material that instead requires electropolishing. </li></ul><ul><ul><li>Buffing offers no improvement in corrosion resistance </li></ul></ul><ul><ul><li>Buffing will in all cases embed grease, adhesives, and any other “dirt” present under a layer of smeared and torn material. </li></ul></ul>
    53. 53. “ Buffing is Not Good” <ul><li>When a high purity surface is required buffing should never be used. </li></ul><ul><li>Proper electropolishing over buffing will remove completely any reflectivity achieved making the practice unnecessary </li></ul><ul><li>End users should insist “no buffing” be performed on any product contact surfaces. </li></ul>
    54. 54. Qualifying Vendors <ul><li>End users are encouraged to develop a program for qualifying an electropolish vendor. </li></ul><ul><li>A good electropolish vendor should be able to produce a procedure for the process used, including independent verification that the procedure used is capable of producing the desired improvements to the micro-surface that have been described during this presentation. </li></ul><ul><ul><ul><li>Featureless micro-surface </li></ul></ul></ul><ul><ul><ul><li>Removal of damaged / heat affected zone </li></ul></ul></ul><ul><ul><ul><li>Optimized corrosion resistance </li></ul></ul></ul>
    55. 55. Bio-Pharm Electropolishing Applications <ul><li>Bio-Pharmaceutical; New, used, and damaged equipment can now be electropolished at the customers facility. Finish problems on product contact surfaces can now be repaired eliminating costly equipment replacement. </li></ul><ul><ul><li>Process Vessels </li></ul></ul><ul><ul><li>Filling Systems </li></ul></ul><ul><ul><li>Piping Systems </li></ul></ul><ul><ul><li>Product Transfer Equipment </li></ul></ul><ul><ul><li>Heated High Purity Water Systems </li></ul></ul><ul><ul><li>Autoclaves and Product Transport Carts </li></ul></ul><ul><ul><li>Freeze Dryer Components </li></ul></ul><ul><ul><li>all can electropolished to enhance cleaning, sterility, rouging characteristics, purity of product </li></ul></ul>
    56. 56. “ In Situ” Vessel Remediation 4000 liter “in place” 316L SS Vessel Agitator Damage Sanded to 320 grit (10 Ra) Bottom Head – Scuffs & Rouge Sanded to 320 grit (10 Ra)
    57. 57. “ In Situ” Vessel Remediation 4000 liter “in place” 316L SS Vessel Agitator Damage – Sanded, Electropolished Bottom Head & Entire Vessel Electropolished
    58. 58. Vessel Remediation Wiper/Scrapper Damage, Never Electropolished Operator Damage, Scratches 200 Liter Portable Vessel – Never Electropolished
    59. 59. Vessel Remediation 200 Liter Portable Vessel 316L
    60. 60. WFI Systems <ul><li>2007 – After four (4) years in service twin 80K Liter vessels were inspected and the customer reported no rouge was present in the vessels! </li></ul><ul><li>These vessels have never required de-rouging or passivation since being Electropolished! </li></ul>
    61. 61. Vessel Remediation Size (Liters) Description of work 5,790 Removed minor scratches and electropolished the entire interior surface 726 Removed minor scratches and electropolished the entire interior surface 6,828 Electropolished the entire interior surface 3,900 Electropolished the entire interior surface 200 Removed minor scratches and electropolished the entire interior surface 726 Removed minor scratches and electropolished the entire interior surface 9,250 Removed very deep pitting and electropolished the entire interior surface 22,000 Removed very deep pitting and electropolished the entire interior surface 30,800 Removed very deep pitting and electropolished the entire interior surface 20,000 Removed very deep pitting and electropolished the entire interior surface
    62. 62. CONCLUSION <ul><li>ELECTROPOLISHING OFFERS THE BEST POSSIBLE PRODUCT CONTACT SURFACES ON EQUIPMENT AND COMPONENTS FABRICATED FROM NICKEL ALLOYS. </li></ul><ul><li>Properly performed electropolishing delivers; </li></ul><ul><li>• Removal of any damaged, work hardened, heat effected zone. </li></ul><ul><li>• Removal of any embedded non-alloy material deposited during </li></ul><ul><li>the manufacturing processes. </li></ul><ul><li>• Microscopic featureless surface </li></ul><ul><li>Allows a very uniform passive layer due to the micro smoothness </li></ul><ul><li>and lack of peaks, valleys, raised grain boundaries, etc. </li></ul>
    63. 63. Electropolishing Why Bother? Electropolishing Why Bother?
    64. 64. To Passivate or Not To Passivate ? That is the Question <ul><li>ASME BPE-2007 defines passivation as “a final treatment/cleaning process used to remove free iron or other anodic contaminates from the surfaces of corrosion- resistant steel parts such that a uniform passive layer is obtained.” </li></ul>
    65. 65. Constructing a Passive Film <ul><li>Passivation is the term used to describe the removal of impurities from the surface of chromium steel after the steel has been worked or formed to produce an item. </li></ul><ul><li>PASSIVATION MAY BE ACHIEVED BY: </li></ul><ul><li>ELECTROPOLISHING </li></ul><ul><li>ELECTROCHEMICAL CLEANING </li></ul><ul><li>CHEMICAL PASSIVATION </li></ul>
    66. 66. Passivation via Electropolishing <ul><li>The electropolishing process removes iron and nickel from the metal surface to a depth of some 20-30 angstroms (depending on exposure time). The result is a uniform film of chromium oxide across the metal surface. </li></ul><ul><li>Electropolishing provides the most uniform and durable passive film that it is possible to achieve. </li></ul><ul><li>If passivation is to be accomplished using electropolishing the procedure must include a final cleaning of the electropolished surface with nitric or citric acid to remove any insoluble (in water) residue. </li></ul>
    67. 67. Electrochemical Cleaning ECC <ul><li>This technique is an extremely effective process. It utilizes specifically formulated abstraction chemistry in conjunction with electrolysis. To some degree it replicates electropolishing however it is a process that removes only the readily soluble passive film contaminates such as iron, nickel, aluminum (grinding residue, etc.) </li></ul><ul><li>If passivation is to be accomplished using electrochemical cleaning the procedure must include a final cleaning of the surface with nitric or citric acid to remove any insoluble (in water) residue. </li></ul>
    68. 68. Chemical Passivation <ul><li>Chemical passivation is used to remove residues from the alloy surface. There are a number of approaches that may be taken. In each case the objective is to remove surface residues that may affect the passive film structured by chemical treatment. </li></ul><ul><li>Chemical passivation is most commonly used when electropolishing or ECC is not practical due to limited access to the surfaces requiring passivation. </li></ul>
    69. 69. Standard Treatment Process <ul><li>DI Water Flush </li></ul><ul><li>Derouging with Organic Acid Intensifiers and Reducing Agents (phase optional based on presence of rouge) </li></ul><ul><li>High Purity Water Rinse </li></ul><ul><li>Decontamination with Alkaline and/or Detergents </li></ul><ul><li>High Purity Water Rinse </li></ul><ul><li>Citric/Chelant Passivation </li></ul><ul><li>High Purity Water Rinse </li></ul><ul><li>Oxidizer or Sanitization with Peroxides </li></ul><ul><li>Final High Purity Water Rinse </li></ul>
    70. 70. System Passivation - Yes or No? <ul><li>Even if The Components are Mill Passivated This is an Essential Step </li></ul><ul><li>The Cr/Fe ratio Must be >1.5 For Best Performance </li></ul><ul><li>Typical Orbital Welds Have Cr/Fe Ratios of 0.11 Plus High Manganese + Silicon </li></ul><ul><li>Unless the Cr/Fe Ratio is Increased and the Mn + Si is Reduced, The Corrosion Resistance Will be Reduced </li></ul><ul><li>Therefore, System Passivation is Essential </li></ul>
    71. 71. Weld Seam Analysis Before Passivation millimeters Article By: K. Balmer Heat Affected Zone
    72. 72. Weld Seam Analysis After Passivation millimeters Article by: K. Balmer Heat Affected Zone
    73. 73. ESCA Tests on 316L Passivation Time <ul><li>Passivation Systems: Commercial Citric Acid system </li></ul><ul><li>Performed on Weld of 316L EP Tubing </li></ul>
    74. 74. Passivated and Non-Passivated Tube Sections - Salt Spray Test
    75. 75. Cleaning Processes Passivation Process Process Description Chemistry Conditions of Process Pros Cons Cleaning Processes Phosphate cleaners Blends of sodium phosphates (TSP,DSP,MSP) and surfactants 1 to 2 hours at 60 to 80 degrees C Removes light organic deposits Can leave phosphate surface contamination Alkaline cleaners Blends of non-phosphate detergents, buffers and surfactants 1 to 4 hours at 40 to 80 degrees C. Can be designed for specific organic contaminates Caustic cleaners Blends of sodium and potassium hydroxides and surfactants 1 to 2 hours at 60 to 80 degrees C Effective at removal of heavy organic contamination
    76. 76. Passivation Process Passivation Process Process Description Chemistry Conditions of Process Pros Cons Passivation Process Nitric acid 10 to 40% active nitric acid 30 to 90 minutes at ambient temperatures Proven method. ASTM recommended and can be run at ambient temps Generates hazardous waste Phosphoric acid 5 to 25% phosphoric acid 1 to 4 hours+ @ 40 to 80 degrees C Effective at removing iron oxides in addition to iron Phosphoric acid blends 5 to 25% citric acid + either citric or nitric acid at various concentrations 1 to 4 hours+ @ 40 to 80 degrees C Can be used at a variety of temperatures and conditions Citric acid 10% citric acid 2 to 4 hours at 40 to 80 degrees C Specific for iron removal. Takes longer to process than mineral acid systems Chelant systems 3 to 10% citric acid with various chelants, buffers, and surfactants 2 to 4 hours at 60 to 80 degrees C. Should be run at elevated temps. Takes longer to process than mineral acid systems
    77. 77.
    78. 78.
    79. 79. Referenced Specifications <ul><li>ASTM A 380 </li></ul><ul><ul><li>Standard Practice for Cleaning, Descaling and Passivation of Stainless Steel Parts, Equipment and Systems </li></ul></ul><ul><li>ASTM A 967 </li></ul><ul><ul><li>Standard Specification for Chemical Passivation Treatments for Stainless Steel parts </li></ul></ul><ul><ul><li>ISPE Baseline Pharmaceutical Engineering Guide, volume 4: Water and Steam Systems </li></ul></ul><ul><li>ASTM B 912-02 </li></ul><ul><ul><li>Standard Specification for Passivation of Stainless Steel Using Electropolishing </li></ul></ul><ul><li>Semi F19 </li></ul><ul><ul><li>Specification for the Surface Condition of the Wetted Surfaces of Stainless Steel Components </li></ul></ul>
    80. 80. Referenced Specifications(cont.) <ul><li>European Hygienic Equipment Design Group Doc 18 Aug. 1998 </li></ul><ul><ul><li>Passivation of Stainless Steel – R.R. Maller; 3-A and EHEDG </li></ul></ul><ul><li>SAE AMS QQ-P-35 (Fed Std QQ-P-35C) </li></ul><ul><ul><li>Passivation Treatments for Corrosion-Resistant Steel, Federal Standard/Specification </li></ul></ul><ul><li>MIL-STD-753C </li></ul><ul><ul><li>Corrosion Resistant Steel Parts: Sampling, Inspection and Testing for Surface Passivation </li></ul></ul>