锌-镍合金电镀层性能及耐腐蚀机理研究

Performance and Anti-Corrosive Mechanism of Electroplated Zn-Ni Alloy Coating

通过X射线衍射、盐水浸泡、盐雾试验和极化曲线测试,对高速电镀Zn-Ni合金镀层钢板的性能进行了检测,主要检测了镀层的耐蚀性能、磷化性能、涂装性能、焊接性能,并对其耐蚀机理进行了初步探讨。试验结果表明,5%NaCl溶液浸泡试验生红锈时间Zn-Ni合金镀层是纯锌镀层的2.5～4.0倍,而且以Ni含量为13%为最好;磷化性能均优于冷轧板;涂装性能、焊接性能均达到工艺要求。在验证防蚀机理的同时,还发现在腐蚀过程中起钝化作用的不是Zn-Ni合金镀层中Ni的富集,而是腐蚀产物的隔离。

The corrosion resistance,phospha-ting performance,hull-painting performance,and welding behavior of the steel plates coated with high-speed electroplated Zn-Ni alloy coating were investigated making use of X-ray diffraction a-nalysis,salt water immersion test,salt-spray test,and measurement of the polarization curves.The anti-corrosion mechanisms of the coatings were primarily explored.It was found that the Zn-Ni alloy coating showed better corrosion resistance than the galva-nized coating in the aqueous solution of 5%NaCl.Namely,no red rust was observed on the Zn-Ni alloy coating immersed in the salt water unless the immersion time rose to 2.5-4.0 times of that of the galvanized coating in the same salt water,and the alloy coating with 13%Ni(mass fraction) showed the best corrosion resistance.Moreover,the steel plates coated with the Zn-Ni alloy coating had better adaptability to phosphating than the cold-rolled counterparts,and the former had satisfactory hull-painting performance and welding behavior as well.With respect to the anti-corrosion mechanisms,the passivation of the electroplated Zn-Ni alloy coating during the corrosion process was not attributed to the enrichment of Ni but to the isolating action of the corrosive products.