The study of corrosion stability of organic epoxy protective coatings on aluminium and modified aluminium surfaces

Abstract

Revestimentos de epóxido foram obtidos através da eletrodeposição catódica de uma resina epóxi sobre alumínio e superfícies de alumínio modificadas (fosfatadas, cromadas-fosfatadas e anodizadas) usando o método potenciostático (concentração da resina de 10% em massa, temperatura de 27 °C e tensão de 250 V). A corrosão desses revestimentos foi investigada durante exposição ao NaCl 3% usando espectroscopia de impedância eletroquímica (EIS) e medidas de polarização. A partir da medida da dependência da resistência, da capacitância e da permissividade, obtida da EIS, e da velocidade da reação de desprendimento de hidrogênio no banho de eletrodeposição, obtida das curvas de polarização, pode-se observar que o revestimento epóxido sobre o alumínio e superfícies de alumínio modificadas constitui uma boa barreira ao transporte de agentes corrosivos. O tempo de contato entre o eletrólito e a superfície do alumínio sob o revestimento é muito maior no caso das superfícies modificadas por cromagem-fosfatização e anodização.Epoxy coatings were formed by cathodic electrodeposition of an epoxy resin on aluminium and modified aluminium surfaces (phosphatized, chromatized-phosphatized and anodized aluminium) using a constant voltage method (resin concentration 10 wt.%, temperature 27 °C, applied voltage 250 V). The corrosion behavior of these coatings was investigated during exposure to 3% NaCl using electrochemical impedance spectroscopy (EIS) and polarization measurements. From the dependence of resistance, capacitance and relative permittivity of the coating, obtained from EIS, on the rate of hydrogen evolution reaction in the electrodeposition bath, obtained from polarization curves, it can be observed that the epoxy coating on aluminium and modified aluminium surfaces is a good barrier against the transport of corrosive agents. The time corresponding to contact between electrolyte and aluminium surface under the coating is greater in the case of surface modification by chromato-phosphatized and anodized aluminium than in the case of phosphatize one.

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Atomic Layer Deposited TiO2 and Al2O3 Thin Films as Coatings for Aluminum Food Packaging Application

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Evaluation of Corrosion Stability of Water Soluble Epoxy-Ester Primer through Electrochemical Studies

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