铝含量对热浸镀锌合金耐蚀性的影响

Influence of Al Contents on Corrosion Performance of Hot-dip Zinc Alloys

采用光学显微镜、电化学测试、SEM等方法研究了Zn-4Al,Zn-5Al和Zn-6Al热浸镀锌合金的显微组织和耐蚀性。结果表明,Zn-4Al合金由Zn-Al层片状共晶组织和大量的初生β-Zn相枝晶组成,Zn-5Al合金为Zn-Al共晶组织加少量的初生β-Zn相组成,Zn-6Al合金为初生的块状α-Al相和Zn-Al共晶组织组成,块状α-Al相周围的共晶组织多为颗粒状。Zn-5Al合金的自腐蚀电流密度J_(corr)最小,极化电阻R_p最大,合金表现出最好的耐腐蚀性。Zn-4Al和Zn-5Al合金是由初生的β-Zn相被优先选择腐蚀,Zn-6Al合金是由块状的α-Al相周围的共晶组织被优先选择腐蚀。

The microstructure and corrosion performance of analyzed by optical microscopy, electrochemical tests, scanning Zn-4Al, Zn-5A1 and Zn-6A1 galvanized alloys were electron microscopy and so on. The results show that the microstructure of Zn-4A1 alloy was composed of lamellar Zn-A1 eutectic and lots of primary α-Zn phase. The microstructure of Zn-5A1 alloy was Zn-A1 eutectic and a little primary β-Zn phase. Besides Zn-A1 eutectic, a few massive α-Al primary phase was discovered in Zn-6At alloy, and the Zn-A1 eutectic around primary α-A1 phase was mostly granular. The electrochemical tests show that the corrosion current density Jcorr of Zn-SA1 alloy was the least, and the electrode polarization resistance Rp of Zn-SA1 alloy was the largest, so the corrosion performance of Zn-SA1 alloy was the best. The corrosion of Zn-4A1 and Zn-5A1 alloy occurred preferentially at the primary β-Zn phase, and the corrosion of Zn-6A1 alloy occurred preferentially at Zn-A1 eutectie around primary a-A1 phase.