Effect of Plasma Sprayed Coatings on Stress Corrosion Cracking of 08Cr2AlMo Steel in Saturated H<sub>2</sub>S Solution

Abstract

Three kinds of coating materials, namely Al2O3, Al2O3(87%)-TiO2(13%), and Cr2O3(92%) -TiO2(3%)-SiO2(5%), were plasma sprayed on specimens of 08Cr2AlMo steel. The corrosion performance of the specimens was determined by potentiodynamic polarization test, slow strain rate tensile (SSRT), and scanning electron microscope (SEM). The test results indicate that the plasma sprayed coatings do not show passivation in saturated H2S solution, but they have higher corrosion resistance than the bare 08Cr2AlMo steel. Furthermore, these coatings reduce SCC susceptibility of the steel in saturated H2S solution. The specimens treated by plasma spray have longer fracture time and larger area reduction. The SCC resistance depends largely on coating porosity, coating type and the bond strength between the coating and the substrate. Among the three coatings, the Cr2O3(92%)-TiO2(3%)- SiO2(5%) coating exhibits the lowest SCC susceptibility.