A comparative study of the anticorrosive performance of different phosphate pigments

R. ROMAGNOLI; L. HERNÁNDEZ; G. BLUSTEIN; C. DEYÁ; B. DEL AMO; V. VETERE

Cartagena de Indias, Colombia

Congreso; LATINCORR 2000. 7th Ibero-American Congress of Corrosion and Protecion, 4th NACE Latin-American Region Corrosion Congress; 2000

The long awaited reduction in the employment of classic active pigments has induced considerable search for suitable alternative products for more than 15 years. Particular attention has been paid to zinc phosphate (first generation phosphate pigments) which effectiveness could be improved by particle size modification or changing its chemical composition with suitable elements such as molybdenum, aluminium, etc. (second generation phosphate pigments). The objective of this work was to  make a comparative study of the anticorrosive properties of different phosphates belonging to the first and the second generation phosphate pigments. Several phosphate pigments were selected: zinc phosphate, zinc molybdenum phosphate, zinc aluminium phosphate, etc. Their  efficiency as anticorrosive pigments was evaluated  in solvent borne paints with 30% v/v of the pigment and a pigment volume concentration/critical pigment volume concentration ratio (PVC/CPVC) equal to 0.8. The behaviour of paints formulated with different binders such as epoxy,  and alkyd resins, has been assessed by accelerated (salt spray cabinet and humidity cabinet) and  electrochemical tests (corrosión potential, ionic resistance and polarisation resistance). It could be seen clearly that the employment of second generation phosphate pigments could improve notably paints performance. As a general rule, it could be said that good correlation was obtained between salt spray and electrochemical tests.