ASTM B322-1999(2014) Standard Guide for Cleaning Metals Prior to Electroplating《电镀前金属清洗的标准指南》.pdf

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1、Designation: B322 99 (Reapproved 2014) Endorsed by AmericanElectroplaters SocietyEndorsed by NationalAssociation of Metal FinishersStandard Guide forCleaning Metals Prior to Electroplating1This standard is issued under the fixed designation B322; the number immediately following the designation indi

2、cates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of

3、 the U.S. Department of Defense.INTRODUCTIONThis guide is intended to illustrate general principles of cleaning prior to electroplating. It is notmeant to apply to every specific application. In specific cases, cleaning practice may depart from thegeneral principles given in this guide.1. Scope1.1 T

4、his guide describes the procedure for cleaning metalsurfaces to obtain good adhesion of electrodeposited metals.The degree of cleanliness required for metals to be electro-plated is greater than for most other finishes. Methods ofremoval of heat-treat or mill scale are not included in thesemethods,

5、because they are covered in practices referring tospecific metals. It should also be understood that while theseprocedures are broadly applicable, particular substrates mayrequire certain specific cleaning procedures.1.2 Adequate cleaning requires a proper combination ofcleaning procedures. The choi

6、ce of these procedures must bebased on a knowledge of the metals to be cleaned and of thesoils to be removed. Because most experience and knowledgein cleaning have been obtained by suppliers of proprietaryprocesses and formulations, these sources should be consultedbefore setting up a cleaning proce

7、ss.1.3 A treatment to remove tarnish, light rust, fingerprints, oroxides is usually provided before immersion of the piece in theelectroplating tank. This treatment activates the metal and isusually accomplished in acid baths which also serve toneutralize the residual alkaline film from alkaline cle

8、aning.Alkaline chelated derusting and cleaning solutions, alone orwith sodium cyanide, used as a soak or electrocleaner, are oftenpreferred before electroplating on ferrous alloys.1.4 Invariably several stages are necessary to provide ad-equate cleaning. These stages are discussed in three parts:Par

9、t IPrecleaning (use of a solvent, emulsion, or alkalinespray) to remove the bulk of the soil.Part IIIntermediate (alkaline) cleaning.Part IIIFinal electrocleaning, to remove trace solids andespecially adherent impurities.Part IVTrouble shooting.Often, depending largely on the amount and type of soil

10、 onthe workpieces as received, one or more of these stages may beeliminated or modified. Usually, even with light soils, it isadvisable to retain multistage cleaning, thereby increasing thelife and efficiency of the cleaning solutions.1.5 This standard does not purport to address all of thesafety co

11、ncerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. (For more specificsafety precautionary statements see Sections 11 and 16.)2. Si

12、gnificance and Use2.1 The performance and quality of electroplated articlesdepend upon the surface cleanliness and condition. Variousmetals are electroplated for decorative or engineering finishes.The common electroplates applied are usually copper, nickel,and chromium for decorative and functional

13、uses. Electro-plated articles are used in many industries such as the marine,automotive, plumbing fixtures, and appliance industries.3. Nature of the Soil3.1 Some of the soils commonly encountered in electroplat-ing are:3.1.1 Solid buffing compounds containing waxes, fattyacids, and abrasives.3.1.2

14、Liquid buffing compounds.3.1.3 Drawing and stamping compounds including thosecontaining fillers (pigments).1This guide is under the jurisdiction of ASTM Committee B08 on Metallic andInorganic Coatings and is the direct responsibility of Subcommittee B08.02 on PreTreatment.Current edition approved No

15、v. 1, 2014. Published November 2014. Originallyapproved in 1958. Last previous edition approved in 2009 as B322 99(2009). DOI:10.1520/B0322-99R14.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.4 Machining oils.3.1.5 Rust-preventi

16、ve slushing oils or greases.3.1.6 Electroplaters stop-off residues.3.1.7 Fingerprints.3.1.8 Dry dirt from storage or dry pickling smut formedduring derusting by pickling.3.1.9 Rust or oxide scales, especially admixed with oil,including heat-treat scales after oil quenching.3.1.10 Phosphate coating w

17、ith or without lubricant.3.1.11 Smut resulting from improper vapor degreasing ofheavily buffed work.3.1.12 Smut resulting from annealing parts without pre-cleaning between drawing operations.3.1.13 Heat-treating salts, with or without quenching oils.3.2 Consideration should be given to control of th

18、e soil. Forexample, efforts should be made to avoid overbuffing, leavingexcessive compound on the work, or aging of the compound onthe part before cleaning. Substitution of liquid for solid buffingcompound, if work permits, often gives easier cleaning, ifproperly applied, but may require use of a di

19、fferent type ofcleaner. Drawing compounds with polymerizing oils or whitelead pigment are to be avoided because of difficulty incleaning. Additives for lubricating and sulfurized cutting oilsare chosen for their ability to adhebe tenaciously and aredifficult to remove. Prolonged storage or drying of

20、 emulsiondrawing compounds after metal working should be avoided sothat slimy water-in-oil emulsions do not form. In-processcleaning or even a hot-water flush before storage is helpful.Emulsion machining lubricants (soluble oils) should be used inplace of sulfurized cutting oils if operations permit

21、. Lower-viscosity machining and rust-preventive oils are more easilyremoved. Stop-off materials, when used, should be appliedcarefully in order to avoid contaminating significant surfaces.The use of clean gloves should be mandatory after buffing orpolishing to avoid fingerprints on the work. Airborn

22、e contami-nants can be avoided by using covers over stored work. It isdesirable to perform a cleaning operation as soon as possibleafter metal forming, polishing, or buffing to reduce the de-mands on subsequent cleaning operations, because many soilsare more easily removed when fresh.4. Metal4.1 The

23、 properties of the metal and the method of fabrica-tion and handling of parts play a role in cleaning. The softnessand surface finish of the metal are factors in selecting handlingmethods. The chemical activity of the metal is an important anddetermining factor in cleaner selection. Aluminum require

24、scare to avoid overetching in alkaline cleaners; both aluminumand zinc are sensitive to pitting attack, zinc and brass totarnishing. Zinc die castings have surfaces that require specialcare because of sensitivity to attack by cleaning solutions. Ifpossible, design of parts should avoid small indenta

25、tions thattend to trap solid particles or buffing compositions. With diecastings, care must be exercised to avoid cutting through thesurface by excessive buffing. The subsurface is usually moresensitive than the“ skin” of the casting. Some surface defectsmay not show up until cleaning and electropla

26、ting cycles arecompleted.5. Cleaner5.1 It is essential that proper cleaners and operationalconditions be selected. Attention should be given to properprocurement since, even in the same category, not all cleanersare equally effective. A cleaner may be very effective for onegroup of soils, yet poor f

27、or other soils. This is true ofelectrocleaners as well as soak or spray cleaners. Soil, type ofwater, available time, rinsing facilities, type of metal, heating,and agitation available, facilities for disposal of cleaner, andtype of personnel and equipment all influence the selection ofcleaners. Obv

28、iously, economics must be considered but aninitial or per pound cost must be balanced against other factors.5.2 Cleaners do not work effectively indefinitely. The effec-tive life of a cleaning bath must be estimated and bathsdiscarded when exhausted. Bath life is influenced by some ofthe factors men

29、tioned above as well as by the volume of workprocessed. The concentration of the cleaner should be con-trolled by analysis at regular intervals.6. Rinses6.1 Water hardness, acidity or alkalinity, and impurities areimportant factors in rinsing (1).2Distilled or demineralizedwater is preferred where i

30、mpurities in rinse water must be keptto a minimum. Boiler condensate may also be used advanta-geously. If the plant conditions water for acidity or alkalinitycare must be taken to be sure the solids content is not too high(Note 1). Impurities derived from processing cannot be ig-nored; that is, rins

31、e waters must be changed frequently oroverflowed continuously (Note 2). Counterflowing rinses are adistinct advantage in obtaining good rinsing with economicaluse of water.NOTE 1Boiler waters which contain cationic corrosion inhibitors maybe quite detrimental to the plating process.NOTE 2Floating oi

32、l on water can cause poor adhesion.7. Equipment7.1 It is important to provide enough room in the plant foran adequate cleaning cycle. A discussion of equipment isbeyond the scope of this practice (2, 3).8. Criteria of Cleanliness8.1 This subject has been treated exhaustively in the litera-ture (4).

33、The atomizer test is the most sensitive one, but thewater-break test is most commonly used. This involves visualobservation after a final rinse in clear, cool water. A continuoussheet of water on the part usually indicates a clean surface.(Certain precious-metal surfaces, such as gold, may exhibitwa

34、ter break, even though clean.) Some experience is necessaryto judge the appearance of a break in the film of water. Aspecific drainage time, about 30 s, should be used beforeobservation.8.2 A dip in clean, dilute acid and reexamination aredesirable to avoid false water-film continuity due to adsorbe

35、dsoaps. Other methods, including electroplating and testing of2The boldface numbers in parentheses refer to the reports and papers appearingin the list of references at the end of this practice.B322 99 (2014)2the electroplate, should be used occasionally to confirm visualexamination. (One procedure

36、involves scrubbing with pumiceand then comparing the surface produced by this method withthat produced under production conditions.)PART IPRECLEANING9. Purpose9.1 Precleaning is designed to remove a large excess of soil,especially deposits of buffing compound or grease. It is alsouseful in reducing

37、the viscosity of waxes and heavy oils, toenable later cleaning stages to be more effective, or to surroundfingerprints and dry dust with an oily matrix to facilitateremoval by alkaline cleaners.10. Types10.1 Cold solvent, vapor degreasing, emulsifiable solvent,solvent emulsion spray, invert-type emu

38、lsion cleaners, or hotalkaline spray with or without solvent emulsion can be used(5).10.2 Cold Solvent (6)Mineral spirits; trichloroethylene;perchloroethylene; 1,1,1,-trichloroethane (methylchloroform);methylene chloride; or trichlorotrifluoroethane can be used forcold cleaning. Combining these with

39、 hand brushing is excellentbut does not lend itself to production conditions. On the otherhand, simple dipping in solvent is frequently ineffective. Thechlorinated solvents are very effective for many soils, but notas effective in removing soap-based or other solvent-insolublesoils. Before electropl

40、ating, cold cleaning with solvents mustbe followed by additional cleaning such as alkaline cleaning toremove slight oily residues.10.3 Vapor Degreasing (7)Trichloroethylene and, to alesser extent, perchloroethylene, trichlorotrifluoroethane, andmethylene chloride are used for vapor degreasing. In va

41、pordegreasing, the work is usually sprayed with clean solvent orgiven a thorough immersion in boiling or warm solvent formechanical removal of tenacious soil or solids. This is fol-lowed by immersion in cold solvent to cool the parts. Thenfollows exposure to condensation of hot, clean solvent vapors

42、on the work. This final step also removes any last traces of oiland grease and dries the part. For removal of caked-on oils andcompounds, a predip in cool solvent can be used to wet andloosen the soil before the degreasing operation.10.3.1 Vapor degreasing can be used to clean all types ofmetal, inc

43、luding steel, steel alloys, light metal alloys, specialbronze, nonferrous metals, nickel, and titanium. This methodsimplifies the cleaning of parts containing several metalsbecause it cleans by solvent action instead of chemical action;there is no danger of over-cleaning or under-cleaning becauseof

44、any difference in chemical activity of the metals present.Because of the rapid penetrating action of the solvent andsolvent vapor, this method is effective in cleaning partscontaining recesses, blind holes, perforations, crevices, andwelded seams. Where the soils are present on surfaces that arenot

45、readily accessible, the process is sometimes supplementedby ultrasonic cleaning in the solvent rinse chamber.10.3.2 Vapor degreasing is effective on solvent-soluble soilsand chemically active lubricants. Insoluble soils (buffing grits,metal chips and dust, etc.) are flushed away as the soluble soils

46、(greases and oils) dissolve in the solvent. It is not effective onmetallic salts, scale, carbon deposits, many inorganic solderingor welding fluxes, and fingerprints unaccompanied by oil orgrease. This process is frequently competitive in cost with wetcleaning methods. Its lower equipment, floor spa

47、ce, and heatrequirements offset the higher cost of solvent.10.3.3 For some applications (steel stampings, buffed zinc-base die castings, etc.), the degreased work can go directly tomild electrolytic cleaning and subsequent electroplating with-out the need for an intermediate alkaline cleaning step.1

48、0.4 Emulsion CleanersOils and high-boiling hydrocar-bons such as kerosene have the ability to dissolve most greases,particularly at high temperatures. The addition of emulsifiers,soaps, and wetting agents enhances the penetrating power ofthe organic solvent and permits removal of the latter andassoc

49、iated soil by power flushing. Further, intimate contact ofthe metal surface with the aqueous phase permits removal ofmaterials not soluble in the hydrocarbon phase.10.4.1 The principle of emulsion cleaning can be applied ina variety of ways including the use of straight emulsifiablesolvents, unstable emulsions (diphase cleaners), invert-typeemulsion cleaners, and stable emulsions. Additions of rustinhibitors or of alkali cleaners can be made to the water phase.Since agitation is important to good cleaning, the power-spraycleaners find wide applications.10.4.2 Emulsion clea