1、Designation: B 912 02Standard Specification forPassivation of Stainless Steels Using Electropolishing1This standard is issued under the fixed designation B 912; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis
2、ion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This specification covers the passivation of stainlesssteel alloys in the 200 (UNS2XXXX), 300 (UNS3XXXX), and400 (UNS4XXXX) ser
3、ies, and the precipitation-hardened al-loys, using electropolishing procedures.NOTE 1Surface passivation occurs simultaneously with electropolish-ing under proper operating conditions. The quality of passivation willdepend on the type of stainless steel, the formulation of the electropol-ishing solu
4、tion, and the conditions of operation. Free iron on the surfaceof the stainless steel is removed resulting in improved corrosion resis-tance. Surface smoothing obtained by electropolishing will also improvecorrosion resistance. Electropolishing will also remove heat tint and oxidescale.1.2 This spec
5、ification may involve hazardous materials,operations, and equipment. This specification does not purportto address all of the safety concerns, if any, associated with itsuse. It is the responsibility of the user of this standard toestablish appropriate safety and health practices and deter-mine the
6、applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:A 380 Practice for Cleaning and Descaling Stainless SteelParts, Equipment, and Systems2A 967 Specification for Chemical Passivation Treatmentsfor Stainless Steel Parts2B 117 Practice for Operating Salt Spr
7、ay (Fog) Apparatus3B 322 Practice for Cleaning Metals Prior to Electroplating4B 374 Terminology Relating to Electroplating4B 602 Test Method for Attribute Sampling of Metallic andInorganic Coatings4D 3951 Practice for Commercial Packaging52.2 ISO Standards:ISO 2080 Electroplating and Related Process
8、esVocabulary6ISO 4519 Electrodeposited Metallic Coatings and RelatedFinishesSampling Procedures for Inspection by At-tributes6ISO 9227 Corrosion Tests in Artificial AtmospheresSaltSpray Tests6ISO/DIS 15730 Metallic and Other Inorganic CoatingsElectropolishing as a Means of Smoothing and Passivat-ing
9、 Stainless Steels6,7ISO/DIS 16348 Metallic and Other Inorganic CoatingsDefinitions and Conventions Concerning Appearance63. Terminology3.1 Definition of terms in this specification can be found inTerminology B 374 and ISO 2080.3.2 Definitions:3.2.1 passivation, nThe rendering of a stainless steelsur
10、face into a lower state of chemical reactivity.3.2.1.1 DiscussionPassivated surfaces are characterizedby the absence of free iron, as defined by Practice A 380.3.2.2 electropolishing, nthe electrochemical process inwhich the article(s) to be passivated are treated anodically in asuitable acid medium
11、.4. Ordering Information4.1 When ordering articles to be electropolished in con-formance with this standard, the purchaser shall state thefollowing:4.1.1 Alloy DesignationWhen ordering articles passivatedin accordance with this specification, the purchaser shall state,in addition to the ASTM designa
12、tion number, the date of issue,the alloy designation number, and the testing method(s) bywhich the article will be evaluated (see 5.3).4.1.2 AppearanceThe purchaser shall specify the appear-ance required, for example, bright or dull. Unless otherwisespecified by the purchaser, a bright luster shall
13、be acceptable.Alternatively, samples showing the required finish, or range offinish, shall be supplied or approved by the purchaser. Whenrequired, the basis material may be subjected, before elec-tropolishing, to such mechanical polishing as may be requiredto yield the desired final surface characte
14、ristics.4.1.3 Contact MarksVisible contact marks may occur.The location of electrical contact marks shall be agreed upon1This specification is under the jurisdiction of ASTM Committee B08 onMetallic and Inorganic Coatings and is the direct responsibility of SubcommitteeB.08.07on Chromate Conversion
15、Coatings.Current edition approved Sept. 10, 2002. Published November 2002.2Annual Book of ASTM Standards, Vol 01.03.3Annual Book of ASTM Standards, Vol 03.02.4Annual Book of ASTM Standards, Vol 02.05.5Annual Book of ASTM Standards, Vol 15.09.6Available from American National Standards Institute, 11
16、W. 42nd St., 13thFloor, New York, NY 10036.7This standard is not a requirement but can be referenced for additionalinformation.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.between purchaser and supplier.4.1.4 Metal RemovalSome met
17、al is removed from thesurface of the article during electropolishing, typically 5 to 10m. As much as 50 m may be removed for additionalsmoothing. The ordering document shall include the maximumamount of metal to be removed.4.1.5 Any requirement for certificationSee Section 9.4.1.6 Any requirement fo
18、r packagingSee Section 10.5. Product Requirements5.1 Visual DefectsWhen specified, the significant surfacesof the article to be passivated by electropolishing shall be freeof clearly visible defects such as pits, roughness, striations, ordiscoloration when examined with 20/20 eyesight at a distanceo
19、f approximately 0.5 m.NOTE 2Defects in the surface of the basis material such as scratches,porosity, inclusions, and so forth, may adversely affect the appearance andperformance of the article. Visible examination shall include wearingcorrectional glasses if the inspector normally wears them.5.2 Pro
20、cess:5.2.1 Surface PreparationPreparatory procedures andcleaning of the basis material may be necessary; see PracticesA 380 and B 322.5.2.2 ElectropolishingFollowing the preparatory opera-tions, the articles are introduced into the electropolishingsolution for a period of time at the current density
21、 andtemperature required to produce the passive surface andrequired surface finish, if any.NOTE 3A typical electropolishing solution and operating conditionssuitable for many stainless steel alloys is shown in Appendix X1.Proprietary electropolishing solutions are available offering special fea-ture
22、s such as low sludging, better bright throwing power, longer life, orbetter performance with specific stainless steel alloys.NOTE 4Intricately shaped articles may not receive the same degree ofpassivation in recessed area as a result of low-current densities. Increasingtime or overall current densit
23、y, or both, or the use of auxiliary cathodes,may be used to improve electropolishing in these areas and to passsubsequent passivation tests.5.2.3 Post DipArticles withdrawn from the electropolish-ing solution will have a residual film that may adversely affectthe appearance or performance of the pro
24、duct. The preferredmethod of removing this film is by rinsing the articles in aroom-temperature solution of 10 to 30 % v/v nitric acid(specific gravity 1.42, 70 % w/w).5.2.3.1 Where local conditions prevent the use of nitric acid(nitrates) for film removal, other options may be used as longas the ar
25、ticles meet the requirements of 5.3.NOTE 5A 60-g/L solution of citric acid has been used for filmremoval; however, note that this procedure may pose waste treatmentdifficulties. The use of other mineral acids, such as sulfuric or hydrochlo-ric acids, is not recommended as the passive film may be com
26、promised.Neutralization procedures such as immersion in alkaline solutions shouldnot be used as they can have a tendency to “set” the residual film anddetract from appearance and performance.5.2.4 Final RinsingRinsing subsequent to passivation isnecessary to remove all traces of acidified water that
27、 may affectthe appearance and performance of the passive part. Deionizedor distilled water may be used to avoid water spots.5.3 Passivation Testing:5.3.1 Passivation by electropolishing shall be evaluated byone or more of the following test methods (see Section 6 fortest procedures):5.3.1.1 Water im
28、mersion test,5.3.1.2 Humidity test,5.3.1.3 Salt spray test,5.3.1.4 Copper sulfate test, and5.3.1.5 Modified “ferroxyl” test for free iron.6. Test Procedures6.1 Water Immersion Test (Specification A 967)The ar-ticle(s) shall be alternately immersed in distilled water for 1 h,then allowed to dry for 1
29、 h for twelve wet-dry cycles (24 htotal). Failure is indicated by the presence of red rust orstaining as a result of the presence of free iron on the surface.6.2 Humidity Test (Practice A 380, Specification A 967)The article(s) shall be subjected to 100 % humidity at 38 62C in a suitable humidity ca
30、binet for a period of 24 h. Failureis indicated by the presence of red rust or staining as a result ofthe presence of free iron on the surface.6.3 Salt Spray (Fog) Testing (Practice B 117 (ISO 9227)The article(s) shall be subjected to the prescribed test for aminimum of2hinanaccredited cabinet. Fail
31、ure is indicatedby the presence of red rust or staining as a result of thepresence of free iron on the surface.6.4 Copper Sulfate Test (Practice A 380, SpecificationA 967)See Appendix X2. The article is swabbed with anacidified solution of copper sulfate. Failure is indicated by thepresence of a cop
32、per-colored deposit or copper-colored spots,or both. This test is not to be used on martensitic 400 seriesstainless steels.6.5 Modified “Ferroxyl” Test (Practice A 380, SpecificationA 967)See Appendix X3. The article is swabbed with asolution of potassium ferricyanide. Failure is indicated by thepre
33、sence of a dark blue color within 30 s.7. Sampling Requirements7.1 Test Method B 602 (ISO 4519) can be applied tofinishes such as electropolished surfaces.7.2 A random sample of the size required by Test MethodB 602 shall be selected from the inspection lot (see 7.3). Thearticles in the lot shall be
34、 inspected for conformance to therequirements of this specification and the lot shall be classifiedas conforming or not conforming to each requirement accord-ing to the criteria of the sampling plans in Test Method B 602.NOTE 6Test Method B 602 contains four sampling plans for theoriginal inspection
35、 of coated articles. Three are to be used when the testmethods are nondestructive; that is, the test method does not make thearticles nonconforming. The fourth plan is used when the test method isdestructive. If it is not clear whether the test is destructive or nondestruc-tive, the purchaser should
36、 identify which test methods are destructive andwhich are nondestructive. In some instances, both destructive and nonde-structive test methods may exist for the testing of the conformance of afinish to a particular requirement. The purchaser should state which is tobe used.7.3 An inspection lot shal
37、l be defined as a collection ofarticles that are of the same kind, that have been produced tothe same specifications, that have been finished by a singlesupplier at one time, or at approximately the same time, underB912022essentially identical conditions, and that are submitted foracceptance or reje
38、ction as a group.7.4 If separate test specimens are used to represent thearticles in a test, the specimens shall be of the nature, size, andnumber, and be processed as required in the test methods ofthis specification. Unless a need can be demonstrated, sepa-rately prepared specimens shall not be us
39、ed in place ofproduction articles for nondestructive tests and visual exami-nation. For destructive tests, separately prepared specimensmay be used.8. Rejection and Hearing8.1 Parts that fail to conform to the requirements of thisspecification may be rejected. Rejection should be reported tothe prod
40、ucer or supplier promptly and in writing. In case ofdissatisfaction with test results, the producer or supplier maymake a claim for a rehearing.9. Certification9.1 When specified in the purchase order or contract, thepurchaser shall be furnished certification that samples repre-senting each lot have
41、 been either tested or inspected as directedin this specification and the requirements have been met. Whenspecified in the purchase order or contract, a report of the testresults shall be furnished.10. Packaging10.1 If packaging requirements are necessary under thisspecification, they shall be in ac
42、cordance with Practice D 3951.11. Test Report11.1 The test report shall include the following information:11.1.1 A reference to this standard,11.1.2 A reference to the test method(s) used (see 5.3.1),11.1.3 The location(s) of the test area(s) on each specimen,11.1.4 The quantity of specimens tested,
43、11.1.5 The name of the operator and the testing laboratory,11.1.6 The date on which the test(s) was (were) performed,11.1.7 Any circumstances or conditions thought likely toaffect the results or their validity,11.1.8 Any deviation from the test method specified, and11.1.9 The result(s) of the test(s
44、) (see section 6).12. Keywords12.1 electropolishing; passivation; stainless steelAPPENDIXES(Nonmandatory Information)X1. TYPICAL ELECTROPOLISHING SOLUTIONX1.1 Electropolishing MaterialsSulfuric acid, 96 %/w 50 % v/vOrthophosphoric acid, 85 %/w 50 % v/vCurrent density 15 amp/dm2minimumTemperature 75C
45、Time, typical 2 to 4 minCathodes stainless steel, copper, leadX2. COPPER SULFATE TEST (FOR FREE IRON)X2.1 MaterialsCopper sulfate test solution:Distilled water 100 mLSulfuric acid, 96 %/w 0.4 mLCopper sulfate, ACS, (CuSO45H2O)1.6 g(dissolve all ingredients)X2.2 ProcedureUsing a cotton swab, apply th
46、e test solu-tion to a clean area of the passivated surface to be tested,keeping the surface wet for a period of 6 min. The formation ofa copper-colored deposit or copper-colored spots or bothindicates failure. Parts used for testing should be discarded orreprocessed.X2.3 StorageThe test solution sha
47、ll be made up freshevery two weeks.X3. MODIFIED “FERROXYL” TEST (FOR FREE IRON)X3.1 MaterialsPotassium ferricyanide test solution:Distilled water 70 mLPotassium ferricyanide, ACS (K3Fe(CN)6) 1.0 gNitric acid, Reagent Grade 70 6 1 %/w,sp. gr. 1.415 to 1.42030 mL(dissolve all ingredients)X3.2 Procedur
48、eUsing a cotton swab, apply the test solu-tion to a clean area of the passivated surface to be tested. Partsused for testing should be discarded or reprocessed.X3.3 StorageThe test solution should be made fresh daily.B912023ASTM International takes no position respecting the validity of any patent r
49、ights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to
