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

Abstract

In this investigation, the synergism pro moted by zinc hypophosphite in an anticorrosive pigment mixture is reported. This paper describes the anticorrosive behavior of a commercial pigment mix ture containing zinc hypophosphite, reduced levels of zinc phosphate, and zinc oxide. The anticorrosive performance of the pigment mixture was assessed by electrochemical techniques (corrosion potential and linear polarization measurements) employing pigment suspensions. The behavior of each separate component of the mixture was also studied in the same way. 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 paints that were evaluated by accelerated (salt spray and humidity tests) and electrochemical measure ments. Experimental results showed that improved anticorrosion protection is achieved in paints with reduced zinc phosphate contents as a consequence of the synergistic interaction between zinc hypophosphite and the other components of the pigment mixture.