1、Designation: B 912 02 (Reapproved 2008)e1Standard 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, th
2、e year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEThe units statement in subsection 1.2 was corrected editorially in April 2008.1. Scope1.1 This specification cove
3、rs the passivation of stainlesssteel alloys in the 200 (UNS2XXXX), 300 (UNS3XXXX), and400 (UNS4XXXX) series, and the precipitation-hardened al-loys, using electropolishing procedures.NOTE 1Surface passivation occurs simultaneously with electropolish-ing under proper operating conditions. The quality
4、 of passivation willdepend on the type of stainless steel, the formulation of the electropol-ishing solution, 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 al
5、so improvecorrosion resistance. Electropolishing will also remove heat tint and oxidescale.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This specification may involve hazardous materials,operations, and equipment. Thi
6、s 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 applicability of regulatory limitations prior to use.2. Referenced Docum
7、ents2.1 ASTM Standards:2A 380 Practice for Cleaning, Descaling, and Passivation ofStainless Steel Parts, Equipment, and SystemsA 967 Specification for Chemical Passivation Treatmentsfor Stainless Steel PartsB117 Practice for Operating Salt Spray (Fog) ApparatusB 322 Guide for Cleaning Metals Prior t
8、o ElectroplatingB 374 Terminology Relating to ElectroplatingB 602 Test Method for Attribute Sampling of Metallic andInorganic CoatingsD 3951 Practice for Commercial Packaging2.2 ISO Standards:3ISO 2080 Electroplating and Related ProcessesVocabularyISO 4519 Electrodeposited Metallic Coatings and Rela
9、tedFinishesSampling Procedures for Inspection by At-tributesISO 9227 Corrosion Tests in Artificial AtmospheresSaltSpray TestsISO 15730 Metallic and Other Inorganic CoatingsElectropolishing as a Means of Smoothing and Passivat-ing Stainless Steels3. Terminology3.1 Definitions:3.1.1 electropolishing,
10、nelectrochemical process in whichthe article(s) to be passivated are treated anodically in asuitable acid medium.3.1.2 passivation, nrendering of a stainless steel surfaceinto a lower state of chemical reactivity.3.1.2.1 DiscussionPassivated surfaces are characterizedby the absence of free iron, as
11、defined by Practice A 380.3.2 Definitions of Terms Specific to This Standard:3.2.1 Definitions of terms in this specification can be foundin Terminology B 374 and ISO 2080.4. Ordering Information4.1 When ordering articles to be electropolished in con-formance with this standard, the purchaser shall
12、state thefollowing:4.1.1 Alloy DesignationWhen ordering articles passivatedin accordance with this specification, the purchaser shall state,in addition to the ASTM designation number, the date of issue,the alloy designation number, and the testing method(s) bywhich the article will be evaluated (see
13、 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 be acceptable.Alternatively, samples showing the required finish, or range of1This specification is under the jurisdiction of AST
14、M Committee B08 onMetallic and Inorganic Coatings and is the direct responsibility of SubcommitteeB08.07 on Conversion Coatings.Current edition approved April 1, 2008. Published April 2008. Originallyapproved in 2002. Last previous edition approved in 2002 as B 91202.2For referenced ASTM standards,
15、visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New Y
16、ork, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.finish, shall be supplied or approved by the purchaser. Whenrequired, the basis material may be subjected, before elec-tropolishing, to such mechanical
17、 polishing as may be requiredto yield the desired final surface characteristics.4.1.3 Contact MarksVisible contact marks may occur.The location of electrical contact marks shall be agreed uponbetween purchaser and supplier.4.1.4 Metal RemovalSome metal is removed from thesurface of the article durin
18、g 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 for packagingSee Section 10.5. Product Requirements5
19、.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 distanceof approximately 0.5 m.NOTE 2Defects in the surface
20、 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 Process:5.2.1 Surface PreparationPreparatory procedur
21、es 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 andtemperature required to produce the passive su
22、rface 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-tures such as low sludging, better bright throwing pow
23、er, 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 density, or both, or the use of auxiliary cathodes,may b
24、e 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 product. The preferredmethod of removing this film is
25、 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 articles meet the requirements of 5.3.NOTE 5A 60-g/L
26、 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 compromised.Neutralization procedures such as immersi
27、on 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 may affectthe appearance and performance of the p
28、assive 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 immersion test,5.3.1.2 Humidity test,5.3.1.3 Salt sp
29、ray 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 h for twelve wet-dry cycles (24 htotal). Failure
30、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 cabinet for a period of 24 h. Failureis indicated by
31、 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 of 2 h in an accredited cabinet. Failure is indicatedby the presence of red rust o
32、r 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 copper-colored deposit or copper-colored spots,o
33、r 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 thepresence of a dark blue color within 30 s.7. Sam
34、pling Requirements7.1 Test Method B 602 (ISO 4519) can be applied to fin-ishes 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 inspected for conformance to therequiremen
35、ts 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 of coated articles. Three are to be used w
36、hen 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 identify which test methods are destructiv
37、e andB 912 02 (2008)e12which 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 shall be defined as a collect
38、ion 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, underessentially identical conditions, and that are submitted foracceptance or rejection as a group.7.4 If separate
39、 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 used in place ofproduction article
40、s for nondestructive tests and visual exami-nation. For destructive tests, separately prepared specimensmay be used.8. Rejection and Rehearing8.1 Parts that fail to conform to the requirements of thisspecification may be rejected. Rejection should be reported tothe producer or supplier promptly and
41、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 been either tested or inspect
42、ed 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 accordance with Practice D 3951.
43、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,11.1.5 The name of the operato
44、r 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) (see Section 6).12. Keywords
45、12.1 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 75CTime, typical 2 to 4 minCathod
46、es 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 the test solu-tion to a clean ar
47、ea 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 shall be made up freshevery two w
48、eeks.B 912 02 (2008)e13X3. 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 ProcedureUsing a cot
49、ton 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.ASTM International takes no position respecting the validity of any patent rights 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 st
