Effect of pH on the corrosion and electrochemical behavior of 3Cr steel in CO₂ saturated NaCl solution

The effect of pH value of NaCl solution on the corrosion and electrochemical behaviors of 3Cr low-alloy steel was investigated by electrochemical technique and SEM technique. The results showed that the pH value of NaCl solution had great effect on the structure of corrosion product. The corrosion scale had a monolayer and map cracking appears when pH=2 and 3.9. The corrosion product film had a triple structure when pH=6.5.The pH of corrosion media also had apparent effect on the electrochemical behaviors of the Cr low-alloy steel. With pH increasing, the main cathodic reaction of electrode process altered, resulting in the negative moving of the corrosion potential, and by the increasing of the charge transfer resistance, the corrosion current density decreased.