Investigation on the initial atmospheric corrosion of mild steel in a simulated environment of industrial coastland by thin electrical resistance and electrochemical sensors

Abstract

The initial corrosion behaviour of carbon steel in a simulated industrial coastland atmosphere was in-situ monitored by thin electrical resistance (TER) and electrochemical impedance spectrum (EIS) sensors through cyclic wetting and drying test. In contrast to the deposition of NaCl particles, the corrosion of (NH4)2SO4 deposition on carbon steel is totally unique, where the thickness loss of NaCl-contaminated carbon steel presents an “up-ramp” increase, but that of (NH4)2SO4-contaminated shows a sharp increase in the first cycle but a “flat” increase in the subsequent cycles regardless of the (NH4)2SO4 loading density, and the corrosion rate of carbon steel versus the loading density of (NH4)2SO4 presents a power function relationship. Moreover, the thickness loss of carbon steel under mixed NaCl-(NH4)2SO4 particles is higher than that under any lone salt deposition with the same loading density. A higher NaCl ratio in the mixed salts leads to a more serious corrosion loss, indicating that the mixed salts have a synergistic deterioration effect on the corrosion of carbon steel, suggesting that the Cl- ions can destroy the corrosion product layer formed by (NH4)2SO4 particles. Finally, the corrosion loss of carbon steel contaminated by mixed salt obeys a typical power function law against time.