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

摘要

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. Basedon this fact, it was decided the incorporation of stainless steels (SS), especially in parts which areexposed to environment, such as exhaust pipes, where the 409 SS tops the production list and in somecases replaced by the 439 SS. This study makes a comparative performance evaluation between ferriticsteels 409 and 439, in different electrolytes that are important to automotive industry like 5% brine assimulating saline environment, 3.5% sulfuric acid (H2SO4) solution and water as the blank, with thepurpose to identify their corrosion behavior. Given the characteristics of stainless steel 409 and 439, isexpected pitting, so mechanistic electrochemical techniques are used, such as cyclic potentiodynamicpolarization curves and electrochemical noise. The corrosion kinetics indicated that the 439 stainlesssteel in H2SO4 had the highest corrosion rate, while in NaCl the 409 had the highest. Both materialshave a pitting corrosion type in sodium chloride using cyclic polarization curves and electrochemicalnoise techniques for its evaluation.