Electrochemical Corrosion Characteristics of 316L Stainless Steel in Simulated Coastal Gold Mine Wastewater under Different pH

Abstract

The passivation behavior of 316L stainless steel in media simulating acidic coastal mine water solution (ACMW) with pH 4 and coastal mine water (CMW) with pH 7 was evaluated by open-circuit potential, potentiodynamic polarization behaviour and electrochemical impedance spectroscopy (EIS). Scanning electron microscope (SEM) was used to observe and analyze the morphological characteristics of the immersion samples. The open-circuit potential profiles and polarisation curves suggest that the passive film can be formed on 316L stainless steel surface after immersion in ACMW for 7 days, while it takes 30 days to form a stable passivation film in CMW. The corrosion state changed from spontaneous passivation to pitting after immersion in two solutions for about 4 months. During long-term immersion, pitting is controlled by charge transfer and diffusion processes. The corrosion potential and pitting potential of 316L stainless steel in CMW are higher than those in ACMW. Electrochemical impedance spectroscopy confirms that 316L stainless steel has good passivation performance in CMW, and stainless steel is more easily corroded in ACMW. The SEM images further prove that the conclusion of electrochemical test is correct