Non-toxic Anticorrosive Pigments Intended for Applications in High-solids and Waterborne Paints

This paper is focused on the study of low-zinc and/or zinc-free pigments which can be suitable replacement of the most widely used zinc phosphate-based pigments in corrosion protection. The comparison of studied pigments was performed on the basis of corrosion weight looses of steel substrate in the course of accelerated corrosion test. The best results were achieved by an application of anticorrosive pigments which are the synergic combination of effective components, i.e. zinc phosphomolybdate and magnesium/magnesium-calcium oxyaminophosphate. Calcium phosphate showed excellent inhibition in an aqueous medium (probably caused by higher solubility in comparison to unmodified zinc phosphate) and the corrosion protection is composed of cathodic passivation, ion- scavenging and barrier mechanism. The comparable degree of corrosion inhibition was found out in the case of calcium borosilicate which provides anodic protection by means of the formation of stable passivation layer to improve adhesion of paint film to metal substrate. The good corrosion protection was also detected in an extract of calcium-exchanged silica. In the case of calcium-exchanged silica the porous structure, large specific surface and the ability to bind aggressive ions in silica pores lead to the good degree of corrosion protection.