1、Designation: A 967 05e1Standard Specification forChemical Passivation Treatments for Stainless Steel Parts1This standard is issued under the fixed designation A 967; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.e1NOTESection 6.1.1.1 was editorially corrected in Ju
3、ly 2007.1. Scope*1.1 This specification covers several different types ofchemical passivation treatments for stainless steel parts. Itincludes recommendations and precautions for descaling,cleaning, and passivation of stainless steel parts. It includesseveral alternative tests, with acceptance crite
4、ria, for confirma-tion of effectiveness of such treatments for stainless steel parts.1.2 Practices for the mechanical and chemical treatments ofstainless steel surfaces are discussed more thoroughly inPractice A 380.1.3 Several alternative chemical treatments are defined forpassivation of stainless
5、steel parts. Appendix X1 gives somenonmandatory information and provides some general guide-lines regarding the selection of passivation treatment appropri-ate to particular grades of stainless steel. It makes no recom-mendations regarding the suitability of any grade, treatment, oracceptance criter
6、ia for any particular application or class ofapplications.1.4 The tests in this specification are intended to confirm theeffectiveness of passivation, particularly with regard to theremoval of free iron and other exogenous matter. These testsinclude the following practices:1.4.1 Practice AWater Imme
7、rsion Test,1.4.2 Practice BHigh Humidity Test,1.4.3 Practice CSalt Spray Test,1.4.4 Practice DCopper Sulfate Test,1.4.5 Practice EPotassium FerricyanideNitric Acid Test,and1.4.6 Practice FFree Iron Test.1.5 The values stated in inch-pound units are to be regardedas the standard. The SI units given i
8、n parentheses are forinformation only.1.6 The following precautionary caveat pertains only to thetest method portions, Sections 14 through 18 of this specifica-tion: This standard does not purport to address all of the safetyconcerns, if any, associated with its use. It is the responsibilityof the u
9、ser of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A 380 Practice for Cleaning, Descaling, and Depassivationof Stainless Steel Parts, Equipment, and SystemsB117 Prac
10、tice for Operating Salt Spray (Fog) ApparatusB 254 Practice for Preparation of and Electroplating onStainless Steel2.2 Federal Specification:3QQ-P-35C Passivation Treatments for Corrosion-ResistantSteels3. Terminology3.1 Definition of Term Specific to This StandardIt isnecessary to define which of t
11、he several commonly useddefinitions of the term passivation will be used in thisspecification. (See Discussion.)3.1.1 DiscussionStainless steels are autopassivating in thesense that the protective passive film is formed spontaneouslyon exposure to air or moisture. The presence of exogenoussurface co
12、ntamination, including dirt, grease, free iron fromcontact with steel tooling, and so forth, may interfere with theformation of the passive film. The cleaning of these contami-nants from the stainless steel surface will facilitate the spon-taneous passivation by allowing the oxygen uniform access to
13、the surface. The passive film may be augmented by chemicaltreatments that provide an oxidizing environment for thestainless steel surface.3.1.1.1 In this specification, passivation, unless otherwisespecified, is defined as the chemical treatment of a stainlesssteel with a mild oxidant, such as a nit
14、ric acid solution, for the1This specification is under the jurisdiction of ASTM Committee A01 on Steel,Stainless Steel and Related Alloys and is the direct responsibility of SubcommitteeA01.14 on Methods of Corrosion Testing.Current edition approved Sept. 1, 2005. Published September 2005. Originall
15、yapproved in 1996. Last previous edition approved in 2001 as A 967 01e1.2For referenced ASTM standards, 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 AS
16、TM website.3Available from Superintendent of Documents, U.S. Government PrintingOffice, Washington, DC 20402.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.purpose of
17、 the removal of free iron or other foreign matter, butwhich is generally not effective in removal of heat tint or oxidescale on stainless steel. In the case of stainless steels withadditions of sulfur for the purpose of improved machinability,passivation may also include the removal of sulfides from
18、 thesurface of the metal for the purpose of maximizing corrosionresistance.3.1.1.2 The formation of the protective passive film on astainless steel, also called passivation in a more generalcontext, will occur spontaneously in air or other oxygen-containing environment when the stainless steel surfa
19、ce is freeof oxide scale and exogenous matter.3.1.1.3 Chemical treatments, such as sodium dichromatesolutions, may facilitate the more rapid formation of thepassive film on a stainless steel surface already free of scale orforeign matter. Such treatments, also sometimes called passi-vation in common
20、 usage, are designated as post-cleaningtreatments in this specification in order to distinguish themfrom chemical treatments capable of removing free iron fromstainless steels.3.1.1.4 The chemical treatments capable of removing heattint or oxide scale from stainless steel and capable of dissolvingth
21、e stainless steel itself, typically called pickling, are substan-tially more aggressive than treatments used for passivation, asdefined in 3.1.1.1. The surface of stainless steel that has beenpickled is free of scale, free iron, and exogenous foreignmatter, and does not require a separate treatment
22、for passiva-tion as defined in 3.1.1.1. The passivation process defined in3.1.1.2 will occur without further chemical treatment but maybe augmented and improved by the post-cleaning treatmentsdefined in 3.1.1.3.3.1.1.5 Electrochemical treatments, including electropick-ling and electropolishing capab
23、le of removing heat tint or oxidescale from stainless steel and capable of dissolving the stainlesssteel itself, are substantially more aggressive than treatmentsused for passivation, as defined in 3.1.1.1. The surface ofstainless steel resulting from these treatments is free of scale,free iron, and
24、 exogenous foreign matter, and does not require aseparate treatment for passivation as defined in 3.1.1.1. Thepassivation process defined in 3.1.1.2 will occur withoutfurther chemical treatment, but may be augmented and im-proved by the post-cleaning treatments defined in 3.1.1.3.Statements regardin
25、g chemical treatments, unless otherwisespecified, are taken to include electrochemical treatments.4. Ordering Information4.1 It is the responsibility of the purchaser to specify a testpractice appropriate to any particular material and application.This specification was written for the purpose of pr
26、oviding analternative to United States Federal Specification QQ-P-35C.Determination of the suitability of this specification for thatpurpose is the responsibility of the purchaser.4.2 Unless specified by the purchaser, the chemical treat-ment applied to the stainless steel parts shall be selected by
27、 theseller from among the listed passivation treatments.5. Materials and Preparation for Passivation Treatments5.1 The passivation treatments shall be of one or more of thefollowing types. The effectiveness of a particular treatment fora particular grade of stainless steel in a particular applicatio
28、n isdemonstrated by meeting the specified testing requirements:5.1.1 Treatments in nitric acid,5.1.2 Treatments in citric acid,5.1.3 Other chemical treatments, including electrochemicaltreatments,5.1.4 Neutralization, and5.1.5 Post-cleaning treatments.5.2 Materials:5.2.1 The chemicals used for passi
29、vation treatments shallproduce passivated surfaces that meet the requirements of oneor more of the tests of this specification. Attention shall begiven to maintaining adequate volume, concentration, purity,and temperature control appropriate to the size and amount ofstainless steel to be treated.5.2
30、.2 The processor shall maintain a record with regard toconcentration and temperature of the passivation solutionsufficient to demonstrate that the specified passivation condi-tions were maintained for each lot of stainless steel partsprocessed. Such records shall be available for inspection whenspec
31、ified in the purchase order. The processor is not required toreveal the precise composition of proprietary chemical mix-tures but shall maintain a unique identification of the mixturethat will ensure its accurate representation for subsequent use.5.2.3 The processor shall be responsible for the safe
32、 dis-posal of all material generated by this process.5.3 Preparation for Passivation Treatments:5.3.1 The pretreatment methods and procedures used priorto the passivation treatment, including mechanical and chemi-cal methods, singly or in combination, for descaling andpickling, shall be in accordanc
33、e with Practice A 380. Whenelectrochemical cleaning is required, it shall be performed inaccordance with Practice B 254.5.3.2 The resulting pretreated surface shall be substantiallyfree of oil, grease, rust, scale, and other foreign matter.5.3.3 When the final pretreatment of a part includes picklin
34、gof the entire surface of the part, no further passivationtreatment is required prior to testing of the surface unlessspecified by the purchaser.6. Treatments in Nitric Acid Solutions6.1 Passivation Treatment:6.1.1 Stainless steel parts shall be treated in one of thefollowing aqueous solutions and m
35、aintained within the speci-fied temperature range for the specified time.6.1.1.1 Nitric 1The solution shall contain 20 to 25 volumepercent of nitric acid and 2.5 6 0.5 weight percent of sodiumdichromate. The parts shall be immersed for a minimum of 20min at a temperature in the range from 120 to 130
36、F (49 to54C).6.1.1.2 Nitric 2The solution shall contain 20 to 45 volumepercent of nitric acid. The parts shall be immersed for aminimum of 30 min at a temperature in the range from 70 to90F (21 to 32C).6.1.1.3 Nitric 3The solution shall contain 20 to 25 volumepercent nitric acid. The parts shall be
37、immersed for a minimumof 20 min at a temperature in the range from 120 to 140F (49to 60C).A96705e126.1.1.4 Nitric 4The solution shall contain 45 to 55 volumepercent of nitric acid. The parts shall be immersed for aminimum of 30 min at a temperature in the range from 120 to130F (49 to 54C).6.1.1.5 Ni
38、tric 5Other combinations of temperature, time,and concentration of nitric acid, with or without other chemi-cals, including accelerants, inhibitors, or proprietary solutions,capable of producing parts that pass the specified test require-ments.6.2 Water RinseImmediately after removal from the pas-si
39、vating solution the parts shall be thoroughly rinsed, usingstagnant, countercurrent, or spray washes singly or in combi-nation, with or without a separate chemical treatment forneutralization (see 9.1) of the passivation media, with a finalrinse being carried out using water with a maximum total sol
40、idscontent of 200 ppm.7. Treatments in Citric Acid7.1 Passivation Treatment:7.1.1 Stainless steel parts shall be treated in one of thefollowing aqueous solutions and maintained within the speci-fied temperature range for the specified time.7.1.1.1 Citric 1The solution shall contain 4 to 10 weightper
41、cent of citric acid. The parts shall be immersed for aminimum of 4 min at a temperature in the range from 140 to160F (60 to 71C).7.1.1.2 Citric 2The solution shall contain 4 to 10 weightpercent of citric acid. The parts shall be immersed for aminimum of 10 min at a temperature in the range from 120
42、to140F (49 to 60C).7.1.1.3 Citric 3The solution shall contain 4 to 10 weightpercent of citric acid. The parts shall be immersed for aminimum of 20 min at a temperature in the range from 70 to120F (21 to 49C).7.1.1.4 Citric 4Other combinations of temperature, time,and concentration of citric acid, wi
43、th or without other chemi-cals to enhance cleaning, including accelerants, inhibitors, orproprietary solutions capable of producing parts that pass thespecified test requirements.7.1.1.5 Citric 5Other combinations of temperature, time,and concentrations of citric acid, with or without other chemi-ca
44、ls to enhance cleaning, including accelerants, inhibitors, orproprietary solutions capable of producing parts that pass thespecified test requirements. Immersion bath to be controlled ata pH of 1.82.2.7.2 Water RinseImmediately after removal from the pas-sivating solution, the parts shall be thoroug
45、hly rinsed, usingstagnant, countercurrent, or spray washes, singly or in combi-nation, with or without a separate chemical treatment forneutralization of the passivation media (see 9.2), with a finalrinse being carried out using water with a maximum total solidscontent of 200 ppm.8. Treatments in Ot
46、her Chemical Solutions, IncludingElectrochemical Treatments8.1 It is recognized that the purpose of removal of allexogenous matter from a stainless steel surface, including theremoval of free iron, can be accomplished by different media,with potential for benefits to be gained from use of proprietar
47、yskills and art, including proprietary passivation media. Suchtreatments may include externally applying an electrical po-tential on the stainless steel parts, as in the case of electropol-ishing. The suitability of such passivation treatments for use inmeeting the requirements of this specification
48、 shall be deter-mined by the capability of the processed parts meeting thespecified test requirements.8.2 Stainless steel parts shall be treated in a specifiedaqueous solution, with or without externally applied electricalpotential, and maintained within a specified temperature rangefor a time suffi
49、cient for the processed parts to meet thespecified test requirement.8.3 Water RinseImmediately after removal from the pas-sivating solution, the parts shall be thoroughly rinsed, usingstagnant, countercurrent, or spray washes, singly or in combi-nation, with or without a separate chemical treatment forneutralization of the passivation media (see 9.2), with a finalrinse being carried out using water with a maximum total solidscontent of 200 ppm.9. Neutralization9.1 The chemical reactions of the passivating media on thesurface of the stainless steel
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