Zinc-rich powder coatings corrosion in sea water: influence of conductive pigments

The effect of addition of conductive pigments like carbon blacks on the corrosion behavior of zinc-rich powder paints coated steel in artificial sea water was investigated. Open circuit potential measurements were used to characterize the cathodic protection ability and duration. Micro-Raman spectroscopy analysis was performed in order to identify the corrosion products and to follow the penetration of the solution inside the coatings.

Two different effects were pointed out: an increase of the porosity induced by carbon addition and a galvanic action between zinc and carbon pigments. The performance of the powder coatings, strongly improved if the carbon amount is sufficient, was compared to the one reported for solvent-based zinc-rich paints.