ASTM B630-88 (R2021) pdf free download.Standard Practice for Preparation of Chromium for Electroplating with Chromium.
1.1 This practice is intended to serve as a process guide (not as a standard procedure) for producing adherent electrodeposits of chromium on chromium for engineering use.
1.2 Only well-known, generally practical methods using hexavalent chromium plating baths have been included. Some of the newer proprietary chromium plating processes produce chromium plating for which this process is unsuitable. Suppliers of the processes should he consulted.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
4. Preparation of Surface
4. 1 Surface Finishing—The smoothness of the chromium coating before electroplating with chromium should closely approximate the requirements of the finished part. It is usually achieved by appropriate grinding with a diamond wheel.
4.2 Stripping and Basis Metal—With previously electroplated parts where the chromium deposit has been worn through, or where grinding has exposed the basis metal, preferred results are obtained by stripping the remaining chromium completely. However, it is possible to obtain satisfactory deposits on such substrates by careful attention to details in the pretreatment and electroplating process steps.
4.3 Stripping may be done by several methods, including proprietary processes or inhibited hydrochloric acid solution
(10 to 20 % by volume), or anodic treatment at 55 to 800 Aim (5 to 75 AlIt2) in a solution of 35 to 50 gIL (5 to 7 oz/gal) of sodium hydroxide or 60 to 75 gIL (8 to 10 oz/gal) of sodium carbonate at 20 to 25°C (70 to 80°F).
4.4 Process Outline:
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), and
4.4.8 Dry.
5. Procedure
5.1 Cleaning—The following cleaning treatments may be used for all conditions and types of electrodeposited chromium. The choice of the procedures will he governed largely by the condition of the surface.
5.1.1 Precleaning—When considerable amounts of grease and oil are present on the surface. precleaning (emulsion or alkaline spray or soak) is necessary to remove the hulk of the soil.ASTM B630 pdf download.