材料期刊网

目的 铁基粉末冶金零件具有特殊的疏松和多孔结构,在前处理、电镀、钝化等过程中易造成零件孔隙的酸、碱、盐等残留,镀后零件在使用过程中也易出现耐腐蚀性能下降或镀层脱落的现象.因此,对铁基粉末冶金零件孔隙进行封闭是一种提高镀层防腐蚀性能和结合性能的有效方法.方法 采用一种专用的粉末冶金零件水基防锈封闭溶液,对零件孔隙进行前处理前的第一次封闭和前处理后的第二次封闭.其孔隙封闭原理是在镀前处理前,利用水基防锈溶液中的缓蚀剂、钝化剂等成分的扩散、渗透,在孔隙处发生吸附、钝化及沉淀等反应,来减轻或避免前处理过程中接触到的酸、碱等成分在孔隙的残留;再在电镀前处理后,进行第二次防锈水溶液的封闭处理,可进一步强化粉末冶金零件的钝化封闭效果.结果 没有经过防锈水溶液封闭处理的白钝化锌镍合金镀层(滚镀零件),在96 h盐雾试验后,表面出现了轻微的腐蚀;经过一次防锈水溶液封闭处理的锌镍合金镀层,在120 h后出现了轻微的腐蚀;经过二次防锈水溶液封闭处理的锌镍合金镀层,在240 h后未出现腐蚀.结论粉末冶金零件经过这二次封闭处理,再进行电镀Zn-Ni合金及镀层钝化处理,可以有效提高零件表面镀层的耐腐蚀性能和结合性能.

Iron-base powder metallurgy parts are provided with loose and porous structure, hence acid, alkali and salt may be left in pores of the parts easily during such process as pretreatment, electroplating and passivation. In such case, the plated parts were easily subject to corrosion resistance decrease or coating peeling off. Therefore, sealing pretreatment of pores in iron-base powder metallurgy parts can efficiently improve the corrosion resistance and coating adhesion. A special water-based antirust sealing solution for iron-base powder metallurgy parts was applied to the first sealing before pores pretreatment and second sealing after pretreatment. During the first sealing process, inhibitor and passivation agent in this special antirust solution could diffuse and permeate through the pores, and result in chemical adsorption, passivation or precipitation in pores, which could reduce or avoid acid, alkali and salt residue during pretreatment. During the second process, the passivation and sealing effects of the parts were further improved. For white passivated zinc nickel alloy coatings not subject to second sealing treatment with antirust water solution (barrel plating parts), slight corrosion occurred on the surface after 96 h salt spray test; for the Zn-Ni alloy coating subject to first sealing treatment, slight corrosion occurred after 120 h; for the Zn-Ni alloy coating subject to second sealing treatment, slight corrosion occurred after 240 h. The corrosion resistance and adhesion property are both signifi-cantly improved by performing the sealing processes, Zn-Ni coating electroplating and coating passivation.