The reverse plating process often called “electropolishing” is also referred to as electrochemical polishing, anodic polishing, electrolytic polishing, or EP.
The electropolishing process involves an electrical current passing through stainless steel or alloy parts submerged in a sulfuric or phosphoric acid bath mixture to remove a thin metal surface layer.
- Polishes areas inaccessible by other polishing methods
- Improves surface reflectivity and brightness
- Levels micro peaks and valleys for better sterilization (roughly 20-40 micrometers thick)
- Removes surface iron and enhances the chromium/nickel content
- Slightly reduces the part size, if necessary
- Provides a corrosion-resistant surface
- Removes surface discoloration from heat treating and/or oxidation
AC7000 – AUDIT CRITERIA FOR NADCAP ACCREDITATION
AC7108 REV I – NADCAP Audit Criteria for Chemical Processing
- AC7108 Anodize; Hard Anodize and Sulfuric Anodize (Not for Metal Bond) – AC7108/8 must also be selected
- AC7108 Chromate (non-hexavalent)
- AC7108 Passivation
- AC7108 Electropolish
- AC7108 Standalone Cleaning
- AC7108 Descaling
- AC7108 Solution Analysis & Testing – AC7108/4 must also be selected
- General Cleaning & Pre-Cleaning
- Alkaline Cleaning
- Chemical Cleaning
- Titanium Cleaning
- Emulsion Cleaning
- Semi-Aqueous Cleaning
- Solvent Cleaning
- Ovens for Thermal Treatments – Heat Processing; Part Dying
- Stripping of Coatings
- Inorganic Coatings
- Other Stripping
AC7108/4 REV C – NADCAP Audit Criteria for Solution Analysis and Testing in Support of Chemical Processing to AC7108
- Solution Analysis (In Support of AC7108)
- Testing Performed Internally (In Support of the Chemical Process Accreditation)
- B05 – Salt Spray Testing (In Support of Chemical Process Accreditation)
- B06 – Water Immersion / Humidity Testing (In Support of AC7108)
- B09 – Taber Wear Testing (In Support of AC7108)
- B10 – Adhesion Testing (In Support of AC7108)
- B13 – Coating Weight Testing(In Support of AC7108)
- B 14 – Conductivity Testing (In Support of AC7108)
- B15 – Resistivity Testing (In Support of AC7108)
- B16 – Coating Thickness Measurement (In Support of AC7108)
- B23 – Other Testing (In Support of AC7108)
AC7108/8 – NADCAP Audit Criteria for Anodizing (Not for Metal Bond)
- Anodized Aluminum, Hard Anodize
- Anodize Aluminum, Sulfuric Acid
AC7108/11 – NADCAP Audit Criteria for Conversion Coating
- Aluminum, Non-Hexavalent Chrome Alternatives
AC7108/12 REV A – NADCAP Audit Criteria for Standalone Cleaning, Descaling, Passivation, and Electropolishing
Surface Roughness Conversion Chart
|Ra (micrometers)||Ra (microinches)||RMS||CLA (N)||Rt||N||Cut-off Length (in)||Cut-off Length (mm)|
Ra = Roughness Average in micrometers or microinches.
RMS = Root Mean Square in microinches.
CLA = Center Line Average in microinches.
Rt = Roughness Total in microns
N = New ISO (grade) scale numbers.
Cut-off Length = Length required for sample.
|ASTM B912-02||1.1 This specification covers the passivation of stainless steel alloys in the 200 (UNS2XXXX), 300 (UNS3XXXX), and 400 (UNS4XXXX) series, and the precipitation-hardened alloys, using electropolishing procedures||6. Test Procedures 6.1 Water Immersion Test (Specification A967/A967M)— The article(s) shall be alternately immersed in distilled water for 1 h, then allowed to dry for 1 h for twelve wet-dry cycles (24 h total). Failure is indicated by the presence of red rust or staining as a result of the presence of free iron on the surface.||6.2 Humidity Test (Practice A380/A380M, Specification A967/A967M)—The article(s) shall be subjected to 100 % humidity at 38 6 2°C in a suitable humidity cabinet for a period of 24 h. Failure is indicated by the presence of red rust or staining as a result of the presence of free iron on the surface.||6.3 Salt Spray (Fog) Testing (Practice B117 (ISO 9227))— The article(s) shall be subjected to the prescribed test for a minimum of 2 h in an accredited cabinet. Failure is indicated by the presence of red rust or staining as a result of the presence of free iron on the surface.||6.4 Copper Sulfate Test (Practice A380/A380M, Specification A967/A967M)—See Appendix X2. The article is swabbed with an acidified solution of copper sulfate. Failure is indicated by the presence of a copper-colored deposit or copper-colored spots, or both. This test is not to be used on martensitic 400 series stainless steels.|
|ES2005 Rev A (Parker Hanifin Quick Coupler Division)||2.3 The Electropolish process in this spec shall be primarily used to improve appearance and corrosion resistance. 2.4 Unless otherwise specified on the drawing, the material removal shall be .0002" to .0004".||3.1 Parts to be electropolished shall be cleaned by any method that leaves the parts free of oil, grease, rust, scale or other foreign matter without adverserly affecting the base material. 3.2 Electrpolishing may be accomplished by any applicable process provided the finsed product meets the requirements of this spec. 3.3 An electropolished partshall have a smooth, high lustre, uniformly bright surface, free of surface contamination, residual solution and solution stain. 3.4 An electropolished part shall be capable of meeting the applicable quality assurance provision of QQ-P-35C (superceded by ASTM A967-17).||ASTM A967-17 Testing Methods we offer-13.3.1 Practice A—Water Immersion Test (see 14.1), 13.3.2 Practice B—High Humidity Test (see 14.2), 13.3.3 Practice C—Salt Spray Test (see 14.3), 13.3.4 Practice D—Copper Sulfate Test (see 14.4)|
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