The effect of epoxy-polyester sealing of sprayed metal coatings for additional corrosion protection

Abstract

Purpose - The purpose of this paper is to report salt spray testing of epoxy-polyester top-coating applied on Zn-sprayed, Al-sprayed and 85Zn-15Al-sprayed steel samples. Design/methodology/approach - In these tests, steel substrates sprayed with Zn, Al and 85Zn-15Al coatings of different average thicknesses ranging from 120 to 210 mu m were top-coated with an epoxy-polyester sealing layer. The corrosion test was performed with salt solution for over 2,000-h. The degree of damage to the samples was evaluated quantitatively in terms of ratio of scribed to unscribed area of coating. Findings - It was evident that the corrosion resistance of Al-sprayed top-coated surfaces was better than coated Zn-spray or coated 85Zn-15Al-spray systems. As a result, when Al-coated, surfaces were top-coated with polymeric layer, it was found that their surfaces were remarkably unaffected by the salt spray environment. Originality/value - The salt spray measurements indicated that the Al-spray epoxy-polyester polymer double system was more durable than the other two systems (polymeric top-coated Zn-spay, and polymeric top-coated 85Zn-15Al-spray), so far as protection from the chloride salt spray environment was concerned.