Zinc hypophosphite: a suitable additive for anticorrosive paints to promote pigments synergism

M. DEYÁ; G. BLUSTEIN; R. ROMAGNOLI; B. DEL AMO

Journal of Coatings Technology and Research

Springer

Año: 2008

1547-0091

              The synergism promoted by zinc hypophosphite in an anticorrosive pigment mixture is reported as a result of this investigation. This paper describes the anticorrosive behaviour of a commercial pigment mixture containing zinc hypophosphite, reduced levels of zinc phosphate and zinc oxide. The anticorrosive properties of the pigment mixture were assessed by electrochemical techniques (corrosion potential and linear polarization measurements) employing pigment suspensions. The behaviour of each separate component of the mixture was also studied in the same way as the whole mixture. The nature of the protective layer was investigated by scanning electron microscopy (SEM). In a second stage, the anticorrosive properties of the pigment were assessed by incorporating it into alkyd and epoxy anticorrosive paints which were evaluated by accelerated (salt spray and humidity tests) and electrochemical measurements. The electrochemical evaluation of painted steel was carried out employing the electrochemical noise technique, whose possibilities were explored. The morphology and the nature of the protective layer grown under the paint film were also assessed by SEM.             Experimental results showed that, as a consequence of the synergistic interaction between zinc hypophosphite and the other components of the pigment mixture, improved anticorrosion protection is achieved in paints with reduced zinc phosphate contents. The electrochemical noise technique is adequate to monitor corrosion in painted panels and is able to detect corrosion under the paint film from very early stages.