Evaluation of eco-friendly anticorrosive pigments for paints in service conditions

The performance of different replacements for chromates was studied. The anticorrosive properties of seven phosphate-based pigments, a calcium-exchange silica and a ferrite were assessed by electrochemical techniques and formulating solvent-borne paints with epoxy and alkyd resins. Paints contained 30% by volume of anticorrosive pigment, with respect to the total pigment content.The anticorrosive performance of paints was evaluated by accelerated tests (salt spray chamber) and electrochemical essays (corrosion potential and ionic resistance). Outdoor exposure tests were carried out in an urban-industrial environment during 8 years.The anticorrosive performance of the tested paints showed that there is not a clear relationship between the laboratory tests and the outdoors exposition and that none of them, by themselves can predict the behaviour of the paint under service. However, electrochemical essays with pigments may give an orientation about pigment performance in anticorrosive paints. As a general rule, if the pigment reduces notably steel corrosion rate and generates a rather high apparent polarization resistance a good anticorrosive performance may be expected.