Use of LCA to evaluate the environmental benefits of substituting chromic acid anodizing (CAA)

Chromic acid anodizing processes are currently being replaced in many industrial sectors because of the recognized adverse effect on the environment and health of used hexavalent chromium compounds. The environmental impacts of the existing processes must, however, be quantified in order to constitute a baseline against which the environmental performance of potential alternative options could be compared. The whole life cycle of the process should also be taken into account to ensure that the possible chosen solution for eliminating or lowering chromium (VI) emissions would not drastically damage the overall process performance in other environmental areas. In our study, we used a simplified life cycle assessment methodology that only took into account the key environmental issues of the considered industrial sector. Both the scope and the data needs were reduced by focusing only on significant flows and by using a generic database for steps other than the anodizing one. A precise literature review was carried out to evaluate bath atmospheric emissions. The results of the performed assessment confirmed that the only way to efficiently deal with hexavalent chromium compounds is to substitute the electrolyte used in the bath as the most Cr(VI) emissions are caused by other stages than the main one. Other specific issues, such as water and energy consumptions have, nevertheless, to be studied throughout the whole life cycle of the chemical substitute to monitor performance against CAA.