Study on Electrochemical Corrosion Behavior of Plasma Sprayed Al2O3-3%TiO2 Coatings Doped with CeO2 for Long-Term Immersion

The long-term corrosion behavior of Al2O3-3%TiO2 (AT3) coatings doped with1%, 5% and 8% CeO2 prepared by plasma spraying was studied in 5% NaCl solution. The results showed that the protective performance of CeO2-doped coatings was significantly higher than that of undoped coatings, primarily due to the reduction in coating porosity caused by the addition of rare-earth elements. Among the doped coatings, the 5% CeO2-doped coating exhibited the best protective performance. The addition of rare-earth oxides CeO2 reduced the content of γ-Al2O3 in the coating, but when the concentration of CeO2 increased to 8%, the Ce element was rich in the gap of the coating. Excessive CeO2 enriched in the gaps and coexisted more with Ti, and prevented the formation of the AlTi phase, which affected the performance of the coating. Electrochemical and XPS results revealed that an appropriate amount of Ce atoms or CeO2 particles could fill the pores of the coating. During long-term immersion, Ce (IV) was converted to Ce (III), which demonstrated that Ce atoms have high chemical activity in coatings. The thermodynamic calculation results show that more CeO2 particles improved the adsorption of corrosive ions. It indicated that the content of doped rare-earth oxides exceeding 5% would be utilized as an active material in the corrosive process.