火电厂循环冷却水对铜合金的点蚀

以北方某电厂循环冷却水为例,用电化学方法研究了Cl-、SO2-4、S2-和pH值等因素对HSn701-B铜合金管材点蚀的影响.极化曲线表明:在该电厂冷却水水质条件下,该管材的点蚀电位随水样中Cl-浓度的增大而下降,腐蚀电位也随之下降,但钝化电流变化不大,点蚀电位与Cl-浓度关系的表达式为:Eb=61.19-14.83lgCl-];少量SO2-4的加入对铜管的腐蚀有阻碍作用,当溶液中HCO-3]/SO2-4]<0.47时,又有促进作用;S2-的加入使铜管的点蚀电位负移、钝化电流增大;pH值的降低会使管材的点蚀电位负移.

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=61.19-14.83lgCl-]. 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.