Estudo comparativo do desempenho anticorrosivo de tintas epóxi com pigmentos a base de molibdatos e fosfatos

Abstract

Molybdates have been introduced as possible replacement to chromates, as anticorrosive pigment, due to its inhibitive properties, to its low toxicity and the possibility of formation of a conversion film on metallic surfaces similar to the chromate conversion coating. In this work, paints were made with the following pigments: zinc chromate, zinc phosphate, zinc phosphate molybdate and zinc-calcium phosphate molybdate. Besides, formulation without pigments (varnish) and another one only with fillers were prepared. The work consists of a comparative study of the anticorrosive performance of the formulated paints, through laboratory cyclic tests (salt spray) and total immersion. The main techniques employed were open circuit potential, polarization curves and electrochemical impedance. In a general way, the zinc chromate presented best results. However in certain conditions of work, the non-toxic pigments have presented satisfactory results.