Electrochemical evaluation of the oxygen permeability for anticorrosive coatings films

C.I. ELSNER; R.A. ARMAS; A.R. DI SARLI

Portugaleae Electrochimica Acta

Portuguese Electrochemical Society

Año: 1995 vol. 13 p. 5 - 18

1647-1571

The effect of both the type and thickness of three anticorrosive paints used as primers (chloride rubber, vinyl and alkys binders) on the oxygen transport were studied. The permeability coefficient of oxygen was calculated measuring the evolution of DC current with time for coated steel samples immersed in 3% NaCl solution with their oxygen being varied by bubbling either oxygen, air or nitrogen. Before, during and after the immersion period a visual inspection of the coated system was also carried out. The results obtained make it possible to conclude that: a) the polarization of the coated steel and the current flux measurements provide useful quantitative information about the oxygen transport through each coated metal/electrolyte system; b) it was verified that the measured current is due to the oxygen reduction on the coated steel surface and its limiting value is characteristic of the system tested; this value was determined by the oxygen transport through the coating and c) the method  used is simple and allowed the following order for the tested paints, as a function of their protective efficiency: chlorinated rubber > vinyl > alkyd.