Characterization of Niobia-alumina Deposited by the Sol-gel Process on Carbon Steel

The precursor sols of Al2O3 and mixed NbxOy/Al2O3 oxides were synthesized by the sol-gel process using acetylacetone to control the reaction kinetics of the organometallic oxides in the mixture. The layers of the precursor sols of Al2O3 and NbxOy/Al2O3 were deposited on AISI steel 1020 by manual immersion (dip coating). The lyophilized sols were characterized by X-ray diffraction, thermal analysis and scanning electron microscopy with EDXS before the recoating process. The influence of the ceramic coating of corrosive processes of AISI steel 1020 were investigated by electrochemical measurements. The only identified phase was poorly crystallized boehmite with homogeneous mixture of Al, Nb, O and C ions in mixed NbxOy/Al2O3 oxides. The ceramic layers deposited appeared to have physical and chemical homogeneity and the steel samples with these deposits had lower corrosion potential. However, the precursor sol Al2O3 showed better steel corrosion protection with lower current density, and more corrosive potential.