It is known that there is special interest in the contemporary investigations on conversion treatment of aluminum aimed at promoting its corrosion stability, which is focused on electrolytes on the basis of salts of metals belonging to the group of rare-earth elements. Their application is especially attractive, as it enables a successful substitution of the presently applied highly efficient, but at the same time toxic Cr 6+-containing electrolytes. The present paper presents a study on the influence of the preliminary alkaline activation and acidic de-oxidation of the aluminum surface on the processes of immersion formation of protective cerium oxides films on Al 1050. The results obtained show that their deposition from simple electrolytes (containing only salts of Ce 3+ ions) on the Al surface, treated only in alkaline solution, occurs at a higher rate, which leads to preparing thicker oxide films having a better protective ability. In the cases when the formation of oxide films is realized in a complex electrolyte (containing salts of Ce 3+ and Cu 2+ ions), better results are obtained with respect to the morphology and protective action of cerium oxides film on samples that have been consecutively activated in alkaline solution and deoxidized in acidic solution. Electrochemical investigations were carried out in a model corrosion medium (0.1 M NaCl); it was shown that the cerium protective films, deposited by immersion, have a cathodic character with regard to the aluminum support and inhibit the occurrence of the depolarizing corrosion processthe reaction of oxygen reduction.

The recently increased interest toward the modification of anodized aluminum oxide (AAO) layers has motivated the present systematical research. The experiments were comprised of three groups of AA1050 alloy samples: preliminary treated, anodized and further AAO layer modification, using AC-assisted silver incorporation. The respective impact of the surface treatment was assessed using different analytical methods, in order to obtain systematical information on the variation of the surface properties, morphology and performance of the obtained Al-O-Ag films. The analyses included determination of the sample color, hydrophobicity and mechanical strength. These measurements were followed by characterization of their morphology by scanning electron microscopy and composition by energy dispersion X-ray analysis and X-ray photoelectron spectroscopy. These characterizations were completed by the assessment of the samples’ performance, after 168 hours of exposure to a 3.5% NaCl model corrosive medium. The corrosion evaluation tests included electrochemical impedance spectroscopy and potentiodynamic scanning. The comparative analysis of the acquired results has enabled us to do a comprehensive description of the mechanism of the AC-assisted Ag-incorporation and its impact on the modified AAO films. The obtained Al-O-Ag functional layers have shown remarkable reliability, being appropriate for various industrial applications.

The corrosion-protective influence of eco-friendly ceria conversion coatings deposited on Al-1050 alloy, additionally treated in mixed NaH₂PO₄ and Ca(NO₃)₂ solution, was studied. The main aim of this work was to investigate how the obtained mixed systems of coatings eliminates the negative role of cracks and pores on the surface formed after deposition only of ceria coating. For this purpose, the growth structure, main components and corrosion resistance of the so formed protective systems were investigated by SEM, EDS, XRD, XPS and electrochemical (PDP, Rp, etc.) methods. The results obtained show that the basic components of the conversion layers (before and after exposure in model corrosion media) are characterized by Al₂O₃, Al(OH)₃, CePO₄ and Ca₅(PO₄)₃(OH). Based on these results, the optimal conditions of immersion treatment(s) of Al substrate are established. At these regimes, the relationship of co-deposited Ce³⁺, PO₄³⁺ and Ca²⁺-containing components of the conversion layers determine the maximum values of their polarization resistance—a basic criterion for corrosion protection of Al. This effect is related to the formation of fill out of the defects of the conversion coatings and additional Ca₅(PO₄)₃(OH), CePO₄ AlPO₄ and Al(OH)₃ deposits, leading to the decrease of the corrosion rate.