Avaliação e comparação da resistência à corrosão por pites do aço super austenítico al 6XN PLUSTM e de um aço inoxidável austenítico AISI 317L.

Abstract

The pitting corrosion resistance of a super austenitic AL-6XN PLUS™ stainless steel (ASA) and of an austenitic 317L stainless steel was investigated using the cyclic polarization technique following the standard ASTM G61-86. These materials were evaluated in the as received condition and heat treated ranging from 500ºC and 900ºC during 72 h. Super austenitic steels are derived from austenitic 317L steel, therefore one can expect a higher corrosion resistance of these steels. No pitting corrosion was observed in the samples of ASA. These results are consistent with electrochemical measurements that show absence of hysteresis in the polarization cyclic curve of ASA. Samples of 317L steel also have a high resistance to pitting corrosion, however, the polarization curves showed hysteresis characteristic of crevice corrosion. There was change in the anodic current to the samples of 317L steel indicating the influence of temperature on the electrochemical tests. Such behavior can be associated with the presence of deleterious phases such as sigma phase coming from the heat treatments.