Influence of Applied Potential on Cavitation Erosion Behavior of Type 316L Stainless Steel in Sulfuric Acid Solution

Abstract

The influence of applied potential on the cavitation erosion (CE) behavior of Type 316L (UNS S31603) stainless steel in 0.05 mol/L sulfuric acid (H2SO4) solution was investigated by using a magnetostrictive-driven CE apparatus. Eight different potentials were selected according to the dynamic polarization curve. Mass loss at different potentials was measured after the tests. Electrochemical impedance spectroscopy (EIS) measurement at different potentials was carried out during each experiment at different intervals. The morphologies of the specimen surfaces were observed using scanning electron microscopy (SEM), and the roughness (Ra) of each surface was measured using a profilometer. The mass-loss results showed that cathodic protection could significantly decrease the CE rate, and the more negative the cathodic potential was, the higher protection efficiency was and the maximum cathodic protection efficiency could be more than 80%. The influence of applied anodic potential on the CE behavior could be classified into three types. First, the CE rate at potentials close to the corrosion potential was almost the same as that at the corrosion potential. The CE rate then decreased a lot in the passive region, and the protection efficiency (89.7%) was even a little higher than that of cathodic protection. Finally, the CE rate increased at higher passive potentials and became very high in the transpassive region. Extremely large electrochemical impedance was shown in the EIS plot at an applied potential of 0.2 V where the best anodic protection was achieved. The SEM, roughness, and EIS results were well in accordance with that of mass loss and provided more detailed information on the CE behavior. A model to describe the effect of the applied potential on CE was proposed.