The assessment of a smart anticorrosive coating by the electrochemical noise technique

Abstract

Zinc phosphate and related compounds are convenient replacements for chromates. However, more eco-compatible pigments are being investigated. The objective of this research was to develop a modified zeolitic rock which is intended to replace phosphate pigments in anticorrosive paints. The modified zeolitic rock was obtained by grinding the rock followed with ionic exchange with molybdenyl ions. This “composite” has an intelligent behavior because molybdenum compounds are leached from the zeolite particle by corrodent species. The anticorrosive properties of this zeolitic rock were studied by electrochemical techniques, employing inhibitor suspensions, and formulating anticorrosive coatings. Coatings performance was evaluated by accelerated tests (humidity chamber and salt spray) and electrochemical noise measurements (ENM). Electrochemical noise data were analyzed in the time domain. The noise resistance (Rn) was compared, as far as possible, with the polarization resistance. It was demonstrated that zinc phosphate content could be reduced to one-third with respect to the recommended value in the literature. The electrochemical noise technique allowed to differentiate the anticorrosive performance of the different coatings formulated in this research. Highlights ► A modified zeolitic rock was tested as anticorrosive pigment in paints. ► Electrochemical noise technique was employed to test the paints. ► Zinc phosphate content could be diminishing employing the modified zeolitic rock as complementary anticorrosive pigment.