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

Abstract

PurposeThe 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/approachIn these tests, steel substrates sprayed with Zn, Al and 85Zn‐15Al coatings of different average thicknesses ranging from 120 to 210 μm 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.FindingsIt 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/valueThe 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.