Microstructure of Trivalent Chromium Conversion Coating on Electrogalvanized Steel Plate

Abstract

The microstructure of trivalent chromium conversion coating on electrogalvanized steel plate has been characterized. The as-deposited coating consisted of three layers with a thin inner layer, a porous intermediate layer, and a thin outer layer. Baking at for 30 min reduced the population density and size of cracks in the coating. Meanwhile, the outer layer became denser, but the immediate layer became highly porous. During baking at elevated temperatures, the chemical species and voids within the coating redistribute, which, in turn, suppresses the formation of microcracks that are commonly seen in the hexavalent chromium counterpart.