含缓蚀剂的镁合金化学镀镍溶液及其所得镀层性能的研究

Study on electroless nickel plating bath with corrosion inhibitor for magnesium alloy and properties of the coating obtained thereby

以AZ91D镁合金为基体,依次进行25 mL/L硝酸+25 mL/L磷酸混合液酸洗及15 g/L NaOH溶液中和,再化学镀Ni–P。化学镀基础配方和工艺条件为:NiSO_4·6H_2O 25 g/L,乳酸28 g/L,NaH_2PO_2·H_2O 30 g/L,硫脲2 mg/L,pH 6.0,温度80℃。镁合金经酸洗、中和处理后表面生成一层薄膜,该膜能缓解镁合金在镀液中的腐蚀。研究了钼酸铵和氟化氢铵作为缓蚀剂对镁合金在镀液中的缓蚀效果。结果表明,两种物质均对镁合金起缓蚀作用。当钼酸铵和氟化氢铵各自以质量分数为1.0%~2.0%和1.5%~2.0%进行复配时,既能减弱镀液对镁合金的腐蚀,又能保证化学镀Ni–P合金的顺利进行。当(NH_4)_2MoO_4和NH_4HF_2以2.0%∶2.0%复配时,镀液的稳定时间和使用周期分别为67 s和4.3 MTO,镀层与基体结合牢固。

Electroless nickel plating was conducted using AZ91D magnesium alloy as substrate, which was acid pickled with 25 mL/L nitric acid ＋ 25 mL/L phosphoric acid followed by neutralization in a 15 g/L NaOH solution. The bath composition and process conditions for electroless nickel plating are as follows： NiSO4·6H2O 25 g/L, lactic acid 28 g/L, NaH2PO2-H2O 30 g/L, thiourea 2 mg/L, pH 6.0, and temperature 80 ~C. A thin film was formed after pickling and neutralization which can relieve the corrosion of magnesium in electroless nickel plating bath. The corrosion inhibition efficiency of ammonium hydrogen fluoride and ammonium molybdate for magnesium in the electroless nickel plating bath was studied. The results showed that both substances have corrosion inhibition effect on magnesium. When ammonium molybdate and ammonium hydrogen fluoride is formulated with a mass fraction of 1.0%-2.0% and 1.5%-2.0% respectively, not only the corrosion of magnesium can be weakened, but also the electroless nickel plating conducted successfully. The stabilization time and service life of the electroless nickel plating bath is 67 s and 4.3 MTO respectively at a （NH4）2MoO4-to-NH4HF2 ratio of 2.0%：2.0%, and the obtained coating bonds strongly to substrate.