Al(OH)_3和Cl^-对稀土铝热浸镀层腐蚀行为的影响

Effect of Aluminum Hydroxide and Cl^- Ion on Corrosion Behavior of Hot Dipped Rare Earth-Aluminum Coating

以自制热浸镀稀土铝为研究对象,采用失重法、极化曲线、SEM和电化学阻抗测试研究了淡水中存在的Al(OH)_3对镀层腐蚀行为的影响;同时,通过极化曲线考察了饱和Al(OH)_3溶液中Cl^-浓度对镀层腐蚀的影响。结果表明:Al(OH)_3能够抑制镀层破损钝化膜的修复,促进阳极活化,诱导镀层点蚀反应的发生,使腐蚀加剧;随Cl^-浓度增加,镀层自腐蚀电流密度先增加后减小,Cl^-浓度为4%时,电流密度最大,镀层耐蚀性能最差。

The corrosion behavior of hot dipped rare earth-aluminum(RE-A1) coating in fresh water with or without Al(OH)_3 was investigated using weight loss test,scanning electron microscopic analysis as well as measurement of polarization curve and electrochemical impedance spectra. At the same time,the effect of Cl^- concentration in saturated Al(OH)_3 solution on corrosion behavior of hot dipped RE - Al coating was examined by measuring polarization curve.Results show that Al(OH)_3 in fresh water can retard the repair of damaged passivation film,accelerate anodic reaction and induce pitting corrosion,resulting in severe corrosion of the RE - Al coating. The corrosion current of the coating initially rose but later declined with increasing concentration of Cl^-.The maximum current density was obtained at Cl^- concentration of 4%, corresponding to the worst corrosion resistance of the hot - dipped RE-Al coating.