Effects of immersion in the NaCl and H2SO4 solutions on the corrosion rate, microstructure, and hardness of stainless steel 316L

Abstract

Stainless steel is one of the materials with excellent corrosion resistance, so it is widely applied in various fields such as the chemical industry, aerospace, power generation, and biomedicine. The environmental condition (neutral, acidic, salty, or basic) is the most important thing to be considered prior to choosing palpable stainless steel materials. In this study, the corrosion behaviors of stainless-steel type SS 316L under exposure immersions in salty and acidic environments using sodium chloride (NaCl) and sulfuric acid (H2SO4) solutions were investigated, by referring to a standard method of ASTM G31-72. Scanning electron microscopy (SEM) results revealed that the specimen in NaCl solution exhibited a darker color, and relatively similar shape of cracks are observed. In contrast, the specimen immersed in H2SO4 was observed to have a large diagonal crack. The corrosion rate of SS 316L immersed in NaCl was lower with a value of 0.4260 mpy, compared to that of H2SO4 which was 2.5141 mpy. The Vickers hardness test showed that the hardness value of NaCl immersion was higher than that of H2SO4, which was 6.34% and 1.94%, respectively. It can be concluded that the SS 316L is better used in a salty environment compared to acidic conditions, because the main function of SS 316L is to be able to withstand rust, one of which is caused by chloride compared to other types of stainless-steel.