氯离子和温度对铝合金在冷却液中腐蚀的影响

分别采用了动电位极化法、电化学阻抗法研究了不同温度下、不同氯离子浓度下防锈铝在模拟冷却液中的腐蚀行为，采用金相显微镜和扫描电镜对极化后防锈铝的表面特征进行了观察和记录。结果表明，氯离子吸附在防锈铝氧化膜表面，对氧化膜表面造成破坏。在一定温度下（30℃），当氯离子浓度超过0.01mol/L时，中间产物吸附作用就会增强，阻抗谱中低频区出现感抗弧，点蚀萌生。随着氯离子浓度增高（超过0.01mol/L），防锈铝的腐蚀加剧，耐腐蚀性能下降。随着温度的升高，阴极和阳极反应阻力变小，阳极金属铝的溶解和阴极氧还原速度增大，腐蚀速度增大。温度升高的同时，溶解氧含量下降，阴极反应受到抑制。与此同时扩散过程在整个腐蚀反应过程中的支配性降低，中间产物在氧化膜表面的吸附作用增强，从而导致低频容抗弧的出现。温度对点蚀形貌的影响主要体现在影响单个点蚀坑的几何大小，促进点蚀坑的生长。

Effect of chloride ion and temperature on corrosion of aluminum alloy in coolant

The effect of chloride concentration and temperature on the corrosion of aluminum alloy in the stimulated coolant was studied by potentiodynamic polarization and electrochemical impedance spectra. The surface characterization of aluminum alloy after polarization was featured by metallurgical microscope and scanning electron microscope. The results show that chloride ions would be involved in the film formation, and decrease the stability of the film. Under a certain temperature (30℃), when the concentration of chloride ion is higher than 0.01 mol/L, the adsorption of intermediate was significant. Inductive loop emerged in the low frequency part of Nyquist diagram, and pits initiate. With the increase of chloride ion concentration (more than 0.01mol/L), the corrosion resistance of aluminum alloy decreased. With the increase of temperature, as the resistance of anodic and cathodic reaction decreased, the rate of anodic and cathodic reaction increased, and corrosion rate increased. When the temperature rose, the dominant effect of diffusion in corrosion process was weakened due to the content of oxygen decreased，the adsorption effect of intermediate was enhanced and inductive loop emerged in the low frequency part. Temperature affects the size of single pit and facilitates the growth of pits.