TEM Analysis and Corrosion Resistance of the Ceramic Coatings on Q235 Steel Prepared by Hybrid Method of Hot-Dipping Aluminum and Plasma Electrolytic Oxidation
The hybrid method of plasma electrolytic oxidation (PEO) and hot-dipping aluminum (HDA) was employed to deposit composite ceramic coatings on the surface of Q235 steel. The cross-section microstructure and surface morphology of the treated specimens were investigated with scanning electron microscopy (SEM). Especially, the composition of the composite coatings was investigated with transmission electron microscopy (TEM). The corrosion resistance was analyzed by immersing and corrosion polarizing experiments. The results indicate that metallurgical bonding can be observed between the ceramic coatings and the steel substrate. There are many micro-pores which act as discharge channels in the PEO coatings. The phase composition of the ceramic coatings is mainly composed of amorphous phase and crystal Al2O3 oxides. The crystal Al2O3 phase includes κ- Al2O3, θ- Al2O3 and β- Al2O3.The corrosion resistance of the PEO samples is much better than that of the HDA samples whether immersed in the NaCl solution or in the sea water.
L. H. Lu et al., "TEM Analysis and Corrosion Resistance of the Ceramic Coatings on Q235 Steel Prepared by Hybrid Method of Hot-Dipping Aluminum and Plasma Electrolytic Oxidation", Applied Mechanics and Materials, Vols. 152-154, pp. 40-45, 2012