Contemporary aspects in the surface treatment of aluminium

A short survey has been made of the existing methods for surface treatment of aluminium aimed at improvement of the corrosion stability of articles of aluminium and its alloys. Special attention has been paid to the methods of preliminary stannate or zincate treatment of the aluminium prior to electrochemical deposition of multilayered metal protective-decorative coatings. A series of issues have been discussed having direct relation to the theory and practice of the immersion treatment processes, whereupon the stress is laid on the factors influencing the kinetics of their formation, respectively their structure and hence the adhesion of the metal coatings, deposited afterwards. Alternative methods of surface modification of aluminium have also been considered, which are used in cases of mild conditions of corrosion attack, namely the methods for the formation of the so called "conversion films" as well as the methods of anodic oxidation that have obtained recently wide application. It has been shown that a special interest is focused, as a tendency in recent studies, on the electrolytes for surface treatment of aluminium and its alloys, which are based on salts of rare-earth metals, aimed at replacing the toxic Cr6+-containing electrolytes. An experimentally established fact has been discussed - the ceria protective films play the role of cathodic coatings with respect to the substrate and they inhibit the proceeding of the cathodic depolarization reaction of the corrosion process. The reviewed literature sources give us the reason to state that the formation of cerium-containing conversion films is one of the most promising alternatives of the chromate conversion films.