Evaluation of the surface treatment effect on the anticorrosive performance of paint systems on steel

C.I. ELSNER; E. CAVALCANTI; O.B. FERRAZ; A.R. DI SARLI

PROGRESS IN ORGANIC COATINGS

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 2003 vol. 48 p. 50 - 62

0300-9440

Electrochemical impedancespectroscopy studies were carried out for paint coated carbon steel sheets under free corrosionconditions when exposed to 3.5% NaCl solution for 405 days. Five anticorrosive primers[epoxy-polyamide/red lead/ferric oxide; alkyd/redlead; epoxy/zinc?aluminium; zinc-richethyl-silicate and epoxy/zinc phosphate] were used while changingthe steel surface treatment condition. The EIS data was interpreted and discussed in terms of the time dependence of the electrical(paint coating) and electrochemical (steel substrate) parametersassociated to interfacial processesdescribing the metal/paint system deterioration. Furthermore, the progress of the coatingdelamination process was estimated by the empirical expression relatingthe measured/specific doublelayer capacitance ratio. Experimental data withdrawn from salt spray cabinet tests performedfor 261 days and adhesionmeasurements are also discussed. On the basis of the electrochemical, visual inspection and standardized tests results it was concluded that the best corrosion performance was provided by the epoxy-polyamide/red lead/ferric oxide anticorrosive paint without any marked effect of the surface treatment; followed by those anticorrosive systems includingdry or wet sandblasting in presence of inhibitor. This result has been attributed to the fact that such surface treatments can improve the barrier properties and/or the inhibitingcorrosion protection and the steel/paint adhesion properties or reduce the osmotic pressure effect.