Trivalent chromium conversion coatings

After prohibiting hexavalent chromium from being used in surface finishing industries, industrial usage of trivalent chromium-based conversion coating has been put into practice. Despite growing interest in the conversion coatings which meet the health and environmental requirements of the directives, published articles on Cr(III)-based conversion coatings are either limited or are mostly done on the propriety products. This literature intends to review the important aspects of these kinds of coatings, using published scientific results. The corrosion performance of the conversion coatings based on Cr(III) is compared with that of Cr(VI). The methods employed to study the coating properties (e.g., composition, morphology, and corrosion resistance) are presented. Furthermore, the impact of process parameters (e.g., pH, temperature, and immersion time) and passivating bath composition are explained by aggregating published investigations. This literature review was carried out employing a manual search of 68 peer-reviewed articles. With the aid of published papers related to the trivalent chromium conversion coating, five main research questions were answered. In the end, this systematic literature review demonstrates the potential remaining questions about Cr(III)-based treatment solution to be studied in the future.