不同表面防护处理的6016铝合金/DC01碳钢电偶腐蚀行为研究

Effect of Surface Treatment on Galvanic Corrosion of 6061 Al-alloy and DC01 Carbon Steel

为探究车用钢铝电偶腐蚀的表面防护工艺效果,分别对车用6016铝合金和DC01碳钢进行钛锆转化和热镀锌处理,采用极化测试、电化学噪声技术和扫描电镜分析不同表面处理的电偶腐蚀速率及腐蚀形态。结果表明:未处理的6016铝合金与DC01碳钢之间存在显著的电偶腐蚀,铝合金作为阳极,偶接24 h就表现出全面腐蚀;仅对铝合金钛锆转化处理,铝合金仍作为阳极,其腐蚀形态以点蚀为主,电偶电流略微降低,防护效果不明显;仅对碳钢镀锌处理,发生极性反转,铝合金转变为阴极受到保护,但铝合金表面富铁夹杂诱发了点蚀坑的形成;对铝合金钛锆转化处理的同时对钢镀锌,电偶电流降低两个数量级,电偶腐蚀防护效果显著。

Surface treatments of titanium-zirconium conversion and hot-dip galvanization were applied on 6016 Al-alloy and DC01 carbon steel, respectively. Then the galvanic corrosion behavior in 5%NaCl solution for the couple of 6016 Al-alloy and DC01 carbon steel without and with pre-surface treatment was comparatively studied by means of polarization measurement, electrochemical noise measurement and scanning electron microscope(SEM). The results showed that the galvanic corrosion between the bare 6016 Al-alloy and bare DC01 carbon steel was severe. The merely titanium-zirconium conversion treatment on 6016 Al-alloy cannot solve the problem of galvanic corrosion of the couple of the surface treated 6016 Al-alloy with bare DC01 carbon steel, while the treated 6016 Al-alloy suffered from pitting corrosion. However, for the couple of bare 6016 Al-alloy and the galvanized steel, the former one could become a cathode, which can be protected by the galvanized steel, whereas, the iron-rich inclusions on 6016 Al-alloy surface induced the formation of pits. However, the galvanic current can be reduced by two orders for the couple of the galvanized DC01 steel and the titanium-zirconium conversion treated 6016 Al-alloy.