Corrosion Behaviour of 304 Austenitic, 15-5PH and 17-4PH Passive Stainless Steels in acid solutions

摘要

The objective of this work was to study is use electrochemical techniques to determinate the growthconditions, characteristics and resistance of passive layers of stainless steel (SS): 304 austenitic, 17-4PH (precipitation hardening) and 15-5PH. Passivation of the SS was performed in 15% citric acid attemperatures of 25 and 49 °C. The corrosion kinetics was obtained using the electrochemical techniqueas potentiodynamic polarization (PP), in a three-electrode system. The electrolytes used were sodiumchloride (5 wt. % NaCl) and sulfuric acid (1 wt. % H2SO4). Passivation in citric acid allows obtainpassive layers at temperatures of 49°C with immersion times of 30 minutes. In precipitation hardeningsteels, passive layers up to 360 mV in sodium chloride. Can be obtained. In sulfuric acid, there is amechanism of passivation – transpassivation - secondary passivation, this due to the highelectropositive values of potential.