Electrochemical Corrosion of Ferritic 409 and 439 Stainless Steels 409 and 439 in NaCl and H2SO4 solutions

Over the time the automotive industry has evolved in the use of steels in different parts of vehicles, thanks to the materials technology; a deciding factor in the market are the corrosion properties. Based on this fact, it was decided the incorporation of stainless steels (SS), especially in parts which are exposed to environment, such as exhaust pipes, where the 409 SS tops the production list and in some cases replaced by the 439 SS. This study makes a comparative performance evaluation between ferritic steels 409 and 439, in different electrolytes that are important to automotive industry like 5% brine as simulating saline environment, 3.5% sulfuric acid (H2SO4) solution and water as the blank, with the purpose to identify their corrosion behavior. Given the characteristics of stainless steel 409 and 439, is expected pitting, so mechanistic electrochemical techniques are used, such as cyclic potentiodynamic polarization curves and electrochemical noise. The corrosion kinetics indicated that the 439 stainless steel in H2SO4 had the highest corrosion rate, while in NaCl the 409 had the highest. Both materials have a pitting corrosion type in sodium chloride using cyclic polarization curves and electrochemical noise techniques for its evaluation.