Influence Factors on Pitting Corrosion of HSn701-B Copper Alloy in Circulating Cooling Water of Power Plant

Taking the recirculated cooling water of a power plant in north China as an example, pitting corrosion behaviors of HSn701-B copper alloy tube was studied in cooling water containing Cl-, SO 2-_4 and S 2- at various pH values by electrochemical methods. Polarization curves reveal that under the conditions of cooling water in the power plant, the pitting potential and corrosion potential of copper tube decrease with the increasing of Cl- concentration, but the passive current changes little. The relation between pitting potential and Cl- concentration is E_b=61.19-14.83lg[Cl-]. A little SO 2-_4 can block the corrosion of copper tube, but will promote the corrosion as [HCO-_3]/[SO 2-_4] is less than 0.47. Adding of S 2- makes the pitting potential moving negatively and passive current increasing. Decreasing of pH values also reduces the pitting potential.