Influence of the surface pre-treatment of aluminum on the processes of formation of cerium oxides protective films

Abstract

Abstract. 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 process -the reaction of oxygen reduction.

Hierarchical Bulk Nanoporous Aluminum for On-Site Generation of Hydrogen by Hydrolysis in Pure Water and Combustion of Solid Fuels

“…As expected, the deconvolution of this Al 2p reveals the predominance of Al–OH peak at ∼74 eV from the Al­(OH) 3 compound . In addition to Al­(OH) 3 , three other Al states were identified: metallic Al peak at ∼72.9 eV, Al–O peak at ∼73.7 eV from Al 2 O 3 , and finally OAl–OH peak at ∼75.2 eV from the AlO­(OH) compound. , The atomic fractions of all these compounds are shown in the inset table of Figure b. The fraction of Al in the form Al­(OH) 3 was found to be 79.31 at.…”

“…metallic Al peak at ∼72.9 eV, Al−O peak at ∼73.7 eV from Al 2 O 3 , and finally OAl−OH peak at ∼75.2 eV from the AlO(OH) compound. 66,67 The atomic fractions of all these compounds are shown in the inset table of Figure 7b. The fraction of Al in the form Al(OH) 3 was found to be 79.31 at.…”

Influence of the Chemical Composition of Ceria Conversion Coatings, Sealed in Solution of NaH2PO4 and Ca(NO3)2, on the Corrosion Behavior of Aluminum

“…The studied specimens/substrates of dimensions 3 × 3 cm were cut out of rolled Al sheets (not polished additionally) with thickness 0.1 cm. Their pre-treatment (in 1.5 M NaOH) is described in [32]; The short name for these pre-treated substrates is S1. The formation of thin conversion ceria oxide coatings on S1 was implemented in a solution containing 0.5 M CeCl 3 × 7H 2 O + 1 × 10 −5 M CuCl 2 × 2H 2 O (at a temperature 25 • C and with a time of immersion 2 h).…”

“…In light of the above, the task of the present study was to establish and juxtapose corrosion behavior, with respect to the efficiency of deposited-on-Al-1050 thin, conversion cerium-oxide coatings (CCOC) [32][33][34][35]. They are subjected to additional sealing posttreatment in mixed solution of sodium phosphate mono basic and calcium nitrate.…”

Electrochemical corrosion resistance of aluminum alloy 6101 with cerium-based coatings in an alkaline environment

“…Conversion coatings have been used in industry for over a century. Conversion coating is a process that changes the surface metal oxide to a coating with different properties that integrates metal cations from the base metal ( Li et al, 2022 ; Campestrini et al, 2004 ; Andreeva et al, 2016 ). The need to include cations originating from the substrate metal is removed by the broader definition.…”