Correlation between accelerated tests and outdoor exposure of coil-coated chromate and chromate free systems

M. ZAPPONI; C.I. ELSNER; F. ACTIS; A.R. DI SARLI

Corrosion Engineering, Science and Technology

Maney Publishing

Lugar: Oxford; Año: 2009 vol. 44 p. 119 - 127

1478-422X

Despite the good corrosion resistance of chromate coatings, there is a general agreement in eliminating the Cr(VI) compounds for corrosion protection owing to their health hazards. Coil coaters are looking for maintained or improved anticorrosion properties. Therefore, coil coated materials painted with conventional polyester topcoat and with either standard strontium chromate or water based epoxy Cr(III) primer were evaluated through a battery of accelerated and outdoor exposure tests. Physicochemical properties, corrosion potential and electrochemical impedance were measured before and after exposure of coated panels in salt spray, humidity or weathering chambers. Experimental results showed that the conventional chromatised polyester primer/polyester topcoat system provides better protective properties than the water base epoxy primer with Cr(III)/polyester system. This was also observed in replicated panels exposed outdoor but just after two years. The protection mechanism was analysed on the basis of the experimental results and the applied formulation type.