镀锌件返工涂覆锌铬涂层工艺探讨

Research on process for reworking the galvanized workpiece by zinc chromate coating technique

锌铬涂覆技术在国内日趋成熟,已被很多制造企业所应用。根据生产现场的需要,通过试验分析,探究出将镀锌零件改制成合格的锌铬涂层零件的工艺案例,解决了镀锌零件上的锌层对锌铬涂层质量的影响问题。采用由硫酸、氯化钠、OP乳化剂组成的酸洗褪锌工艺,须先以抛丸破坏原有锌镀层的完整性,虽成本低,但存在氢脆的危险,不适用于高强度连接件和弹性类零件。采用由氢氧化钠和亚硝酸钠组成的溶液进行碱煮的工艺,适用于所有铁基材料褪锌后涂覆锌铬涂层。2种工艺处理后的零件均满足耐20%硝酸铵快速腐蚀试验时间>1.5h的要求。

Zinc chromate coating technology is getting mature in China, and has been applied to many manufacture corporations. A case for modifying zinc-plated parts to eligible zinc chromate coated parts was given by testing and analysis, based on the requirement of production locale. The influence of zinc deposit on zinc-plated parts on the quality of zinc chromate coating was resolved. The process based on pickling with H2SO4, NaC1, and OP emulsifier for removing zinc deposit needs to destroy the zinc deposit previously by shot blasting, and has a risk of hydrogen embrittlement in despite of low cost, hence is not suitable for high-strength connectors and elastic components. The process based on alkaline boiling with NaOH and NaNO2 can be applied to removal of zinc deposits from all iron-based materials for further zinc chromate coating. The parts treated by both processes can endure more than 1.5 h in accelerated corrosion test with 20% NH4NO3 solution.