炭板阳极对铝合金表面稀土电沉积转化膜性能的影响

Effect of Carbon Hoard and Lead Hoard as Anode Materials on Corrosion Resistance of Elertrndeposited Cerium Salt Convention Coating on Aluminum Alloy Suhslrate

阳极材料对稀土铈盐转化膜性能有较大的影响,采用电解沉积法在防锈铝LF21合金表面形成了一层稀土铈盐转化膜,比较了采用炭板和铅板作阳极材料,对转化膜性能的影响。扫描电镜显示,使用炭板做阳极材料时所形成的转化膜表面裂纹细小且呈线条状,膜层成分中不含Pb元素;极化曲线测试显示,使用炭板所形成转化膜的腐蚀电位比使用铅板所形成转化膜的腐蚀电位正移125 mV,击穿电位正移100 mV。中性盐雾试验结果表明,铅板做阳极时66%的试片能通过7 d的测试,炭板做阳极时的通过率为100%;测试时间达到14 d,前者所有试片均发生点蚀,而后者通过率仍为100%,说明使用炭板所形成的转化膜比使用铅板所形成的膜具有更优良的耐腐蚀性能。

Cerium-based conversion coaling was deposited on corrosion-resisting aluminum alloy LF21 using electrolysis method. The effects of carbon board and lead board as the anode materials on the corrosion resistance of the Ce-hased conversion coaling were investigated using scanning electron microscopy, energy dispersive spectroscopy, polarization curve measurement, and neutral sail-spray lest. It was found that the anode materials had a significant effect on the corrosion resistance of the Ce-hased conversion coaling. The Ce-hased conversion coating prepared using the carbon board anode had small cracks in linear array on the surface and had no Pb. At the same time, it recorded a shift towards positive direction as much as 125 mV and 100 mV, in corrosion potential and pit potential, respectively, as compared with the Ce-based conversion coaling prepared using the lead board anode. Moreover, only 66% of the Ce-based conversion coating samples prepared using the lead board anode were endurable to the neutral salt-spray test up to a duration of 7 days, and none of them was endurable to a duration of 14 days under the same test conditions. However, all the Ce-based conversion coating samples prepared using the carbon board anode passed 14 dav neutral salt-spray test and showed nosigns of corrosion.