Avaliação da resistência à corrosão localizada em aços austeníticos em meio ácido e neutro contendo cloreto

Abstract

Corrosion is a phenomenon quite common in several areas, for example, pipes that can transport acid material, favoring the corrosive process. Some types of steel that are characterized by their greater resistance to corrosion, which are called stainless steels, are currently being used. In this classification, there are two types of steel that have been well studied and used in various sectors: they are austenitic stainless steels and super austenitic stainless steels. The difference between one stainless steel from another is the amount and presence of alloying elements, like molybdenum, chromium, nickel and nitrogen, in a way that super austenitic are steels that have an increase in the chromium and molybdenum content when compared to austenitic, improving their corrosion resistance properties. In order to evaluate and compare pitting corrosion resistance of commercial super austenitic stainless steel AL 6XN PLUS ™ ฀ with austenitic stainless steel 317L, corrosion in both steels was stimulated through a potentiodynamic polarization test, which measures the tendency of a steel to suffer localized corrosion through the use of electrolytes, which, for this work, a solution of 0.5 M H2SO4 + 0.5 M NaCl and another of 0.5 M NaCl was used. One of the results obtained was the comparison between the resistance of the two steels, in which it was possible to confirm the greater resistance to corrosion by the steel AL 6XN PLUS ™ ฀, since it did not suffer localized corrosion, unlike the 317L steel, which presented crevices in both electrolytes. Furthermore, it was also possible to observe that the passivity that the H2SO4 exerts on the surface of steels could also be observed in the tests carried out in this work, since the anodic current densities in the polarization test presented higher values with the use of NaCl when compared with the use of electrolyte of 0.5 M H2SO4 + 0.5 M NaCl.