1、Designation: B630 88 (Reapproved 2017)Standard Practice forPreparation of Chromium for Electroplating with Chromium1This standard is issued under the fixed designation B630; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、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.1. Scope1.1 This practice is intended to serve as a process guide (notas a standard procedure) for producing adherent electrode
3、positsof chromium on chromium for engineering use.1.2 Only well-known, generally practical methods usinghexavalent chromium plating baths have been included. Someof the newer proprietary chromium plating processes producechromium plating for which this process is unsuitable. Suppli-ers of the proces
4、ses should be consulted.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this st
5、andard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles f
6、or theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2B177 Guide for Engineering Chromium Electroplating3. Significance and Use3.1 Electrodeposits of chrom
7、ium on chromium are producedin cases where it is desired to obtain a better performingcoating, to reclaim plated parts that are defective, or restoreworn chromium coatings to original dimensions.4. Preparation of Surface4.1 Surface FinishingThe smoothness of the chromiumcoating before electroplating
8、 with chromium should closelyapproximate the requirements of the finished part. It is usuallyachieved by appropriate grinding with a diamond wheel.4.2 Stripping and Basis MetalWith previously electro-plated parts where the chromium deposit has been wornthrough, or where grinding has exposed the basi
9、s metal,preferred results are obtained by stripping the remainingchromium completely. However, it is possible to obtain satis-factory deposits on such substrates by careful attention todetails in the pretreatment and electroplating process steps.4.3 Stripping may be done by several methods, includin
10、gproprietary processes or inhibited hydrochloric acid solution(10 to 20 % by volume), or anodic treatment at 55 to 800 A/m2(5 to 75 A/ft2) in a solution of 35 to 50 g/L (5 to 7 oz/gal) ofsodium hydroxide or 60 to 75 g/L (8 to 10 oz/gal) of sodiumcarbonate at 20 to 25C (70 to 80F).4.4 Process Outline
11、:4.4.1 Preclean (see 5.1.1 and 5.1.2),4.4.2 Alkaline electrolytic clean (see 5.1.3),4.4.3 Rinse (cold water),4.4.3.1 Rinse (hot water),4.4.3.2 Dry,4.4.3.3 Mask (see 5.2),4.4.4 Activate (see 5.3),4.4.5 Chromium electroplate,4.4.6 Rinse (cold water),4.4.7 Rinse (hot water), and4.4.8 Dry.5. Procedure5.
12、1 CleaningThe following cleaning treatments may beused for all conditions and types of electrodeposited chro-mium. The choice of the procedures will be governed largelyby the condition of the surface.5.1.1 PrecleaningWhen considerable amounts of greaseand oil are present on the surface, precleaning
13、(emulsion oralkaline spray or soak) is necessary to remove the bulk of thesoil.5.1.2 Abrasive CleaningOxide and other films may beremoved by mechanical techniques using such abrasives as fineemery on a cloth or a wheel, pumice slurry, or greaseless1This practice is under the jurisdiction of ASTM Com
14、mittee B08 on Metallicand Inorganic Coatings and is the direct responsibility of Subcommittee B08.02 onPre Treatment.Current edition approved May 1, 2017. Published May 2017. Originallyapproved in 1977. Last previous edition approved in 2010 as B630 88 (2010).DOI: 10.1520/B0630-88R17.2For referenced
15、 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 ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Consh
16、ohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Org
17、anization Technical Barriers to Trade (TBT) Committee.1buffing compounds. Grit blasting, shot blasting, wet blasting,or vapor honing may also be used. Abrasive cleaning isgenerally not necessary when suitable mechanical finishingprocedures have been used.5.1.3 Cathodic Alkaline CleaningRemoval of fi
18、nal tracesof dirt, grease, and oil is best accomplished by cathodicalkaline cleaning. Cathodic electrocleaning is necessary be-cause anodic electrocleaning will strip chromium and mayexpose the basis metal. In cathodic cleaning, the parts arenegatively charged and attract positively charged metallic
19、 ions,soaps, and other colloidal materials in the solution, causingthem to “plate out” as loose smut on the surfaces beingcleaned. Thus, do not allow the cleaning solution to becomeheavily contaminated with dirt, grease, or oil.5.2 MaskingRigid, nonconductive materials or stop-offs,which are especia
20、lly compounded nonconductive tapes, waxes,lacquers, or polymeric materials, will protect areas that are toremain free of chromium. Due to the varying kinds ofchromium electroplating solutions and interactions with thesematerials, vendor instructions should be followed.5.3 Activating:5.3.1 The proced
21、ure used for etching or activating thechromium surface is most important and usually determines thesoundness of the adhesion. Chromium exhibits a strong ten-dency to acquire surface oxides rapidly (air passivity) thatreduce the adhesion of subsequent chromium deposits. Anodicetching in a chromic aci
22、d solution, 250 g/L , at room tempera-ture is recommended. In some instances, this procedure may beperformed in the chromium electroplating solution.5.3.2 Give the part an anodic etch for 5 to 60 s at 6 V. Foreffective control, confirm etch action by visual observation ofuniform gassing; increase et
23、ch time if necessary. When basismetal is exposed or high-speed chromium electroplating solu-tions are used, keep the time as short as possible.5.3.3 When the part to be electroplated has a large mass,allow it to reach the temperature of the electroplating bathbefore etching.5.4 Chromium Electroplati
24、ng:5.4.1 Make the part cathodic up to 3.0 V. Slowly increasethe voltage in steps of 0.25 V so that gassing and electroplatingstart after 30 to 60 s and full current is reached in 5 min.5.4.2 The composition of the ordinary or “conventional”solution is 250 to 400 g/L of chromic acid (CrO3) and sulfat
25、eradical (SO4=) to maintain a ratio by weight of CrO3toSO4=of 100 to 1, although many electroplaters prefer ratios aslow as 80 to 1, which facilitates electroplating chromium onchromium. The sulfate is generally added as sulfuric acid (94to 96 mass % H2SO4). Refer to Guide B177 for more infor-mation
26、 on the operation of the electroplating solution.5.4.3 Some proprietary baths contain a supplementary cata-lyst in the form of fluorides or other mixed catalysts. Some ofthese baths are satisfactory, but some could be unsuitable. Thesupplier of any proprietary bath should be consulted forspecific in
27、formation.6. Keywords6.1 activation; chromium; cleaning; preparation; strikingASTM 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 valid
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30、ot received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple co
31、pies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 88 (2017)2
