Avaliação da resistência a corrosão do aço inoxidável AISI 304 submetido à eletropolimento em meio ácido.

Abstract

In this work we aim to conduct a study about the corrosion resistance of the stainless steel AISI 304 in medium acid. The samples analyzed were previously submitted to an electrochemical treatment called electropolishing. This process is characterized by being anodic in nature, in other words, inverse to electrodeposition. Flat plates of stainless steel AISI 304 were electropolished by applying a fixed charge of 240 C at current densities of 400, 680 and 960 mAdm"2 . After the electropolishing, all samples were semi-gloss, however, the samples processed with higher current densities exhibited marked improvement of homogeneity. These results, observed by visual analysis, became even more evident from the superficial microscopic analyses of the samples. The corrosion tests were made using the Potentiodynamic Linear Polarization (PLP) and Electrochemical Impedance Spectroscopy (EIS) techniques, in the midst of 2M H2SO4 and in duplicate. We evaluated samples submitted to the electropolishing process in different conditions of current densities, as well as samples in their "natural" state, with the aim of comparing the influence of the treatments on corrosion resistance. The results indicated that the technique was effective to increase corrosion resistance by forming a passivation film rich in chromium. It was found that the electropolishing means an important technological process that can be applied to remove unwanted oxides, as well as it can improve the appearance and promote the formation of a layer of chromium oxides, stable and homogeneous in steels AISI 304.