Study on corrosion resistance properties of hydrothermal sealed arc sprayed aluminium coating

Abstract

In this study, traditional hydrothermal sealing (HTS) treatment was for the first time employed to arc sprayed pure aluminium coatings, and proves to be a successful sealing method. Corrosion performances were examined in salt solution immersion test (SSIT) and electrochemical polarisation measurements. The HTS coating is covered with a continuous film of aluminium hydroxide structures, and some deionised water manages to penetrate. Besides, pores in the surface as well as in the inner part get smaller and fewer. In SSIT, the HTS coating has a similar corrosion process to the unsealed one, but corrodes much more slightly. In polarisation curves, the HTS coating exhibits a wide passive region, higher corrosion potential and lower current density than the unsealed coating before immersion. After SSIT, it exhibits small changes in polarisation curves, implying slight corrosion in 90 days immersion and proving much higher corrosion resistance than the unsealed coating in the whole process.