Anticorrosive performance of acrylic-styrene base paints used for steel protection

ELSNER, CECILIA INÉS; DI SARLI, ALEJANDRO R.; AMALVY, JAVIER IGNACIO; AZNAR, ALBERTO CARLOS

San Pablo, Brasil

Congreso; 10° Congreso Internacional de Pinturas ABRAFATI 2007; 2007

ABRAFATI

Among recently developed waterborne coatings, acrylic-styrene base paints occupy a special place. In this paper, the authors show and try of explaining the main experimental results obtained in laboratory tests leading to characterize the anticorrosive properties of steel/waterborne paint systems subjected to either immersion in 0.5M NaCl solution alone or previous aging in weather-Ometer for 700hours, and then immersed in that solution. The binder was prepared in the laboratory by emulsion polymerization of styrene and acrylic monomers. Three ecological pigments were utilized: two phosphate-based and one prepared in the laboratory using a tannin-base recipe. Two levels of PVC were tested. The known and effective zinc tetroxychromate pigment was included as reference. Electrochemical impedance spectroscopy (EIS) was used for electrochemical characterization. From the analysis and interpretation of the experimental results could be inferred that: 1) the water permeability of each painting system was affected by the weathering test; 2) independently of the exposure conditions, the painting systems pigmented with zinc tetroxychromate provided the worst anticorrosive protection; on the contrary, the best was afforded by that pigmented with zinc phosphate and PVC 15%; 3) samples subjected to the weathering test followed by the immersion one showed better anticorrosive behavior. This was attributed to the fact that insoluble products formed during the first step were able of blocking the painting system intrinsic and/or extrinsic defects; and 4) the anticorrosive performance of different painting systems subjected to also different exposure conditions was adequate and widely characterized by means of standardized and electrochemical methods.