STUDY OF THE CHEMICAL FORMATION OF CERIUM OXIDE CONVERSION LAYERS ON ALUMINIUM AD-3

The effect of the concentration of cerium ions as а component of electrolytes, designed for conversion treatment, has been studied in view of the morphology and structure of the conversion films, formed on Al. The studies have been carried out in a complex electrolyte containing cerium and copper ions at temperature 25 оС and duration of the treatment 60 and 120 min. It has been found out that the presence of copper ions in the electrolyte leads to the formation of more compact and richer in cerium conversion films. The electrochemical characteristics (corrosion current, corrosion potential) of the formed films have been investigated applying potentiodynamic polarization method in 0.1 M NaCl solutions. The composition of the electrolytes has been optimized with respect to the concentrations of cerium and copper ions, aiming at obtaining conversion films having improved protection ability. Thereupon the influence of the microgalvanic couples copper/aluminium has been established.