Electrochemical performance of organic zinc-rich coating as an impressed current anode system

Abstract

Cathodic protection is a proven technique to halt or minimise corrosion of steel embedded in concrete structures and bridges exposed to chloride from road dicing salt. Cathodic protection for reinforced concrete has generally been limited to impressed current systems due to the relatively high resistivity of concrete and reduced life of galvanic zinc anodes at high chloride content. Zinc rich paints (ZRP) are widely used as an anti-corrosion paint on steel substrates, an alternative to hot-dip galvanising. A type of vapour-permeable zinc-rich paint made of 96% zinc has been proposed for cost effective and low maintenance impressed current cathodic protection of reinforced concrete structures. To evaluate its potential application in practice, the electrical, and electrochemical properties of the material have been investigated. The zinc-rich anode was found to shift the potential of the steel to more negative potentials successfully and satisfy the performance criteria in accordance with BS EN ISO 12696. In this research it is found that the optimum conductivity will be achieved by three coats to produce 280-320 m thickness in order to get a good current distribution in the surface of the anode.