Cerium conversion coatings on aluminium alloys
Jožef Stefan Institute, Ljubljana, Slovenia
Conversion coatings can be formed on metal surfaces by an electrochemical or chemical process. In the past, the most important coatings used for corrosion protection of aluminium alloys were chromate conversion coatings. Due to their negative impact on the environment and human health, alternatives have been sought in the last decades. Among those, coatings based on cerium (rare earth metal) are chosen to be the focus of this lecture. Both have been investigated for almost 40 years, generating scientific data on the coating formation mechanisms and properties such as their composition, structure, thickness, and corrosion performance. In the first part of the lecture, some basic considerations of the chemistry of Ce salts and the general mechanism of coatings formation will be presented. This will be followed by the examples from our research work on both types of coatings, aiming to point out some specific issues that are still open to further investigation.