THE USE OF SCANNING ELECTROCHEMICAL MICROSCOPY (SECM) TO IDENTIFY ELECTROCHEMICALLY ACTIVE FEATURES IN THERMALLY SPRAYED INCONEL 625 COATINGS

摘要

Inconel 625 is a nickel-based corrosion resistant alloy which is widely used as a thermally sprayed coating to protect components in aqueous corrosive environments. Whilst, such coatings offer a degree of protection, they have inferior corrosion resistance compared to the wrought alloy. Previous work has demonstrated that this difference in corrosion performance is not simply due to interconnected porosity but also involves microstructural features related to oxidation of powder particles during spray deposition of the coating. In recent work, several processing techniques, specifically sintering and laser melting, have been used to deliberately modify the microstructure of the material in order to understand the role of specific microstructural features on the electrochemical behaviour of the coatings. The present study investigates the microstructural features of the coatings, using scanning electrochemical microscopy as a tool to identify the electrochemically active areas. The results are related to the overall corrosion behaviour which is evaluated by salt spray and potentiodynamic testing.