Hard chrome plating and alternative coatings in the automotive industry

Hexavalent chromium coating technology is one of the most sought out electrolytic coating processes adopted in the automotive industry. These coatings possess exceptional corrosion resistance, wear and tear resistance and hardness making them suitable for applications in the automotive industry. However, there has been a growing concern regarding its applications as it accounts for carcinogenic and hazardous properties. Due to this, strict restrictions have been imposed by REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) and EPA (Environmental Protection Agency) in Europe and the USA respectively regarding the usage of hexavalent chromium. As a result, there have been efforts to explore high quality coating techniques that do not depend on electrolysis. This thesis deals with the characterization of hard chrome coatings, mainly hexavalent chromium and trivalent chromium, and other alternative coatings (in view of reducing the usage of hexavalent chromium) such as PVD & CVD, electroless nickel, and heat treatment by gas nitriding process on metal substrates (steel). The primary tests employed to study the coatings were optical microscopy & scanning electron microscopy (EDS) for morphological analysis, neutral salt spray test for corrosion resistance, vicker’s hardness test for evaluating micro-hardness, and again microscopic analysis for thickness inspection. The analysis was carried out at the group materials laboratory of Centro Ricerche Fiat (CRF), Italy. Although, it was already understood that hexavalent chromium will show excellent properties while subjected to these tests, the study was primarily focussed on understanding the behaviour of alternative coatings and how they can be used for various applications in terms of varying functionalities, thus highlighting the need for alternate solutions, all the while giving importanceto sustainability and green manufacturing in the coating processes.