Anticorrosive Performance of Vinyl Butyral-co-vinyl alcohol-co- vinyl Acetate Based Copolymer Adsorbed on Steel Surfaces. Electrochemical and AFM Studies
The copolymer film anticorrosive performance based on poly(vinyl butyral-co-vinyl alcohol-co-vinylacetate), called in this study as PVBA, deposited by the dipping method on the carbon steel and 304Lstainless steel surfaces from methanolic solution was studied by open circuit potential (OCP)measurements, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Themorphological characteristics of the uncovered and covered surfaces with copolymer film, before andafter corrosion were identified by atomic force microscopy (AFM). The average protection performance(P%) of PVBA adsorbed on metallic surfaces corroded in 0.9% NaCl solution reached the value of 64 ±2% for carbon steel and 72 ± 2%, respectively, for 304L stainless steel. AFM 3D images, beforecorrosion, display coherently organized coatings adsorbed on the surfaces of steels, with a networkcharacteristic, more obviously in the case of 304L stainless steel than that of carbon steel. Aftercorrosion, AFM shows that the surface upper-layers preserve their features, suggesting that the coatingremains anchored to the metal surface for a long time, but the polymer swelling in NaCl solution causesthe relative detachment of the film from the substrate, with the formation of some free areas on whichthe oxidation processes can be accelerated, leading to PVBA anticorrosive performance disturbance.
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