超超临界燃煤机组T23钢水冷管的腐蚀行为浅析

Analysis on Corrosion Behavior of Water-Cooling Wall Tube Steel T23 in Ultra-Supercritical Fossil Units

随着超临界、超超临界机组参数的提高和热负荷的增大,其水冷管材料对水中离子的敏感性也越高,其与水中杂质离子的腐蚀行为直接关系到机组的安全运行。采用电化学方法研究了常温下模拟加氧工况溶液中,阴离子对1 000 MW超超临界燃煤机组水冷壁管材料(T23钢)腐蚀行为的影响。结果显示:在模拟加氧工况溶液中无论Cl-和SO2-4是否单独存在,Cl-和SO2-4均加速T23的腐蚀,且随Cl-和SO2-4浓度的增加,T23钢的腐蚀电流升高,腐蚀电位降低,阻抗值降低,腐蚀加速;当Cl-和SO2-4同时存在时,腐蚀比Cl-单独存在时更为严重,应严格控制给水中阴离子以保证机组安全运行。

The influence of anions in simulated oxygenated aqueous solution on the corrosion behavior of water-cooling wall tubing steel T23 of 1 000 MW ultra-supercritical fossil units was investigated by electrochemical techniques at room temperature. Results indicated that,whether in the presence of Cl-and SO2-4 alone or in the coexistence of Cl-and SO2-4,both Cl-and SO2-4 could promote the corrosion of T23 steel. With the increase of concentration of Cl-and SO2-4,the corrosion current of T23 rose,and its corrosion potential and impedance value declined. Beside,in the coexistence of Cl-and SO2-4,the corrosion of T23 steel was more severe than in the presence of Cl-alone. Therefore,it was imperative to strictly control the type and concentration of anions in feedwater so as to guarantee the safe operation of the units.