Anti-corrosion properties of zinc dust paints

Abstract

A model of a bare steel area exposed at a break in a zinc dust paint film has been designed to allow the simultaneous examination of cathodic protection of the steel and the deposition of corrosion inhibitive zinc compounds under immersed conditions. Results indicate that any reduction in zinc area by reducing pigment content or top-coating reduces protection, not by restricting cathodic protection by polarization of the zinc, but by reducing the production of inhibitive zinc compounds. Oxygen and ion permeability measurements on zinc dust paint films have shown only small permeability decreases on ageing, and it is suggested that protection is due to the deposition of inhibitive zinc compounds on steel rather than sealing of the films by zinc corrosion products. © 1977.