The corrosion effect of multiple anions coexistence on grounded metals

Abstract The corrosion behavior of Q235 carbon steel and 304 stainless steel with different ratios of Cl − /SO 4 2− /HCO 3 − was investigated through weightlessness and electrochemical experiments. Under the coexistence of Cl − /SO 4 2− /HCO 3 − , the corrosion current density ( j corr ) of Q235 carbon steel and 304 stainless steel increases compared to when only HCO 3 − is present. Among them, Cl − is trapped in the corrosion pit due to its small radius and strong penetration power, exacerbating pitting corrosion propagation. As the Cl − /SO 4 2− /HCO 3 − ratio increased from 18:3:1 to 6:1:1, the j corr of Q235 carbon steel increased from 8.073 μA·cm −2 to 32.343 μA·cm −2 , accelerating corrosion; When the ratio is further adjusted to 6:1:2, the increase in HCO 3 − content promotes the formation of a dense FeCO 3 layer on the surface, and j corr decreases to 12.862 μA·cm −2 , inhibiting corrosion. For 304 stainless steel, an increase in this ratio will enhance the conductivity of the solution, reduce the activation energy of electron transfer, decrease the charge transfer resistance ( R ct ) from 217.3 kΩ·cm 2 to 15.79 kΩ·cm 2 , increase j corr from 81.729 μA·cm −2 to 1,365.0 μA·cm −2 , and intensify pitting corrosion.