I Fifteen Years of Outdoor Corrosion of Trivalent and Hexavalent Chromium Electrodeposits

hen the first trivalent chromium electroplating process was commercially introduced in the mid-l970s, information on the corrosion properties of the deposits and other physical properties was unknown. To obtain a comprehensive understanding about the corrosion properties of trivalent chromium electrodeposits over a variety of nickel deposits, chromium deposits from trivalent chromium electrolytes were compared to both microdiscontinuous and nonmicrodiscontinuous deposits from hexavalent chromium electrolytes. Deposits from trivalent chromium electrolytes are microdiscontinuous as plated. In order for hexavalent chromium deposits to be microdiscontinuous, special treatments are usually required before or after chromium plating. The data and conclusions obtained from this study apply only to the deposits from the single-cell process introduced in the mid1970s. The properties of deposits from double-cell and other single-cell processes have not been reported. A paper covering the accelerated corrosion properties of the single-cell trivalent chromium process has previously been published.' Covered here are the outdoor corrosion results for deposits on panels electroplated at the same time the panels for the accelerated corrosion study were plated. The physical properties of chromium electrodeposits obtained from the trivalent chromium plating process used in this study and the operating characteristics of this process have been reported previously.2