1、Designation: B630 88 (Reapproved 2010)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.2. Referenced Documents2.1 ASTM Standards:2B177 Guide for Engineering Chromium Electroplating3. Significance and Use3.1 Electrodeposits of chromium on chromium are pro
6、ducedin 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 with chromium should c
7、loselyapproximate 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 basis metal,preferred resul
8、ts 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, includingproprietary processes
9、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:4.4.1 Preclean (see 5.
10、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. Procedure5.1 CleaningThe following
11、 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 (emulsion oralkaline sp
12、ray 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 greaselessbuffing compounds. Grit blasting, shot blasting, wet blasting,1This practic
13、e is under the jurisdiction of ASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility of Subcommittee B08.02 onPre Treatment.Current edition approved Nov. 1, 2010. Published November 2010. Originallyapproved in 1977. Last previous edition approved in 2006 as B630 88 (2
14、006).DOI: 10.1520/B0630-88R10.2For 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 ASTM website.1Copyright ASTM International,
15、100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.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 final tracesof dirt, grease, and oi
16、l 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 ions,soaps, and other colloidal
17、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 especially compounded nonconductive tape
18、s, 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 procedure used for etching or activatin
19、g 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 acid solution, 250 g/L , at room tem
20、pera-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 etch time if necessary. When basism
21、etal 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 Electroplating:5.4.1 Make the part cathodic u
22、p 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 sulfateradical (SO4=) to maintain a rat
23、io 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 on the operation of the electrop
24、lating 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 information.6. Keywords6.1 activati
25、on; 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 validity of any such patent rights, an
26、d 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 revisi
27、on of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you sh
28、ouldmake 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 copies) 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 ASTM website (www.astm.org/COPYRIGHT/).B630 88 (2010)2
