Effect of NaCl on Initial Corrosion Behavior of Q235 Steel

The effect of NaCl concentration and immersion time on the initial corrosion of Q235 steel was studied in laboratory. The results indicate that the critical corrosion concentration of NaCl was 3.5 wt% under the testing conditions. In 3.5 wt% NaCl solution, Q235 steel was more prone to corrosion and the corrosion rate was the largest, and the reaction resistance on the electrode surface was the least. Corrosion current density and surface reaction resistance of Q235 steel fluctuated with time. After 24 hours' immersion in 3.5 wt% NaCl solution, the free-corrosion potential in the corrosion system was the lowest, the corrosion current density and corrosion rate were the largest. Corrosion products on electrode surface had a limited protective effect on the substrate. Loose structure and small adhesion of the corrosion product made it easy to fall off from the electrode surface, and thus the corrosion reaction was accelerated.