Avaliação eletroquímica do mecanismo de corrosão dos aços inoxidáveis austeníticos AISI 304 e AISI 316 em meio salino

Abstract

The phenomenon of natural and spontaneous electrochemical degradation affects mainly metals is known as corrosion and depends on the relationship between medium, material and operating conditions so that it can be characterized and is not an intrinsic property of the material. Thus, this work aims to evaluate the electrochemical relationship between three different materials when immersed in saline solution, namely SAE 1020 carbon steel - used as reference material - AISI 304 stainless steel and AISI 316 stainless steel. Electrochemical analyzes were performed on samples of each of the mentioned metals, when immersed in 0.5 M NaCl solution with an exposed area of 1cm2. Also, metallographic characterization was performed by Scanning Electron Microscopy, before and after immersion for the purpose of monitoring the predominant mechanism of corrosion. Based on the results, it was observed that carbon steel is the most susceptible to corrosion in seawater. On the other hand, AISI 316 stainless steel shown a better performance, regarding the observed degradation mechanism. It was also noted that the predominant localized type corrosion mechanism that occurred in all three specimens was by pitting. Although the two stainless steel samples had better results for the analyzes performed, the AISI 304 steel presented a lower pitting potential and was more susceptible to the degradation mechanism than the AISI 316 steel sample, showing the molybdenum action in the increased corrosion resistance of the material when aggressive.