目的 为了明确层流冷却浊环水中Cl?质量浓度对SPHC钢板腐蚀的影响，提高SPHC钢板在潮湿环境下存放发生腐蚀后的表面质量。方法 通过全浸腐蚀试验进行模拟。已有研究表明层流冷却浊环水中Cl?的质量浓度与钢板表面Cl?的残留量呈线性正比关系，因此设置不同Cl?质量浓度对SPHC钢板的腐蚀行为进行研究。通过数码相机、扫描电镜和激光共聚焦显微镜分析宏观腐蚀形貌和腐蚀坑形貌，采用失重法测量不同Cl?质量浓度下的均匀腐蚀速率，电化学测试分析不同Cl?质量浓度下覆盖腐蚀产物膜试样的电化学特征。结果 Cl?质量浓度为60、300、1 000 mg/L时，均匀腐蚀速率都呈现先增大后减小的趋势，这是点蚀的形成扩展和腐蚀产物的缓蚀作用所致。Cl?质量浓度升高，穿过基体表面的离子增多，缩短了点蚀形成和扩展的时间，均匀腐蚀速率增大。Cl?质量浓度的升高使得基体表面钝化膜被加速破坏，腐蚀电流密度增大，形成的锈层极易被溶解，阻抗值上下波动，这种情况下形成的锈层对基体不具有保护作用。结论 降低层流冷却浊环水中Cl?的质量浓度是提高潮湿环境下腐蚀后SPHC钢板表面质量的有效途径。

The surface quality of steel products has always been a major concern. In the steel rolling process, in order to reduce production costs, laminar flow cooling of steel plates is often performed using recyclable water treated by turbid ring water systems. Due to the rapid evaporation of water during the cooling process, there will be some ions left on the surface of the steel plate, which will make the steel plate corrosive in the later storage process. In order to clarify the effect of the concentration of Cl? in laminar cooling turbid ring water on the corrosion of SPHC steel plates, so as to improve the surface quality of SPHC steel plates after corrosion occurs when they are stored in a humid environment, simulations were performed by full immersion corrosion tests. It was shown that the concentration of Cl? in the laminar cooling turbid ring water showed a linear and positive relationship with the residual amount of Cl? on the surface of steel plates, so the corrosion behavior of SPHC steel plates was studied by setting different concentrations of Cl?. The macroscopic corrosion morphology of the specimens was analyzed by digital camera. The surface morphology and depth of corrosion pits on the specimens were analyzed by scanning electron microscopy and laser confocal microscopy, respectively. The loss-in-weight method was used to measure the uniform corrosion rate for different concentrations of Cl?. Electrochemical tests were performed to analyze the electrochemical characteristics of specimens covered with corrosion product films at different concentrations of Cl?. The results show that whether the concentration of Cl? is 60 mg/L, 300 mg/L or 1 000 mg/L, the uniform corrosion rate shows a trend of increasing first and then decreasing, which is caused by the formation and expansion of pitting corrosion in the early and middle stages of corrosion and the corrosion retardation of corrosion products in the late stages of corrosion. The increase in the concentration of Cl? increases the number of ions crossing the surface of the substrate, shortening the time for pitting to form and expand, and increasing the uniform corrosion rate. Although the accelerated corrosion rate will also accelerate the formation of corrosion products, the high concentration of Cl? will destroy the protective effect of corrosion products on the substrate. The analysis of the polarization curve shows that the increase of the concentration of Cl? makes the passivation film on the surface of the substrate be accelerated and destroyed, and the corrosion current density increases. In addition, the impedance value fluctuates at the high Cl? concentration, indicating that the rust layer formed is easily dissolved, and this rust layer does not have a good protective effect on the substrate. Therefore, the concentration of Cl? in the turbid ring water needs to be reduced in order to reduce the residual amount of Cl? on the surface of the steel plate. In summary, reducing the concentration of Cl? in laminar cooling turbid ring water is an effective way to improve the surface quality of SPHC steel plates after corrosion in a humid environment.