Study on the Corrosion Resistance of Supersonic Plasma Spraying Al2O3 Thin Layer and SiO2 Sealer Alternately Deposited Coating

Abstract

The longevity of thermally sprayed ceramic coatings is often difficult to achieve in corrosive environments. In this paper, an alternating sealing coating technology was used to seal supersonic plasma sprayed Al2O3 coatings. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the coating microstructure of Al2O3 coatings and seal coats. The corrosion behavior of alternating sealing coating, traditional sealed coating, and spray coating at 5 wt.% NaCl was studied by the electrochemical test method (dynamic polarization) and immersion corrosion experiments. The results show that the alternating sealing coating is better in preventing the production of through holes and hindering the inward diffusion of corrosive media than traditional sealed coatings, and further increases the thickness of the sealing layer. Compared with the traditional sealing coating, the porosity of alternating sealing coating is decreased by 70.5%, the corrosion potential is increased by 74 mV, and the corrosion current density is decreased by about 78%, which confers better long-term corrosion resistance.