NH_4HF_2对AZ31镁合金化学镀镍层性能的影响

Influence of NH_4HF_2 on Property of Electroless Ni-P Plating on AZ31 Magnesium Alloy

采用增重法、精密pH计、扫描电镜(SEM)和动电位极化曲线测定和分析了镀液的镀速、镀液的缓冲性、镀层的表面形貌和镀层的耐蚀性,研究了不同浓度NH_4HF_2对AZ31镁合金化学镀镍层性能的影响.结果表明,NH_4HF_2的浓度影响镀液的镀速及缓冲性、镀层的形貌及耐蚀性.当NH_4HF_2的质量浓度为5～15 g/L时,镀速随浓度的增加递增,而当NH_4HF_2的质量浓度为15～25 g/L时,镀速随浓度的增加而减少;镀液缓冲性随NH_4HF_2浓度的增加而提高.当NH_4HF_2的质量浓度为15 g/L时,镀速达到最大值21.9μm/h;当NH_4HF_2的质量浓度为20 g/L时,镀层致密完整且阳极极化曲线的钝化电位区间最大,自腐蚀电流密度最小,因此,此时镀层的耐蚀性最好.

Influence of different contents of NH_4HF_2 on property of electroless Ni-P plating on AZ31 magnesium alloy was studied.Plating rate and buffering of electrolyte,morphology and corrosion resistance of coatings were studied by means of mass gain method,accurate pH gauge, SEM and potentiodynamic polarization curve etc.Results showed that the addition of NH_4HF_2 greatly affected the plating rate and the bath stability,so that the morphology and corrosion resistance of the plated coatings.When the content of NH_4HF_2 in range 15～25 g/L,the plating rate increased with the increase of content of NH_4HF_2;When the content of NH_4HF_2 in range 15～20 g/L,the plating rate decreased with increase of NH_4HF_2;while buffering of bath electrolyte increased with increase of NH_4HF_2.When the content of NH_4HF_2 was 15 g/L the plating rate reached a maximum 21.9μm/h.When the content of NH_4HF_2 was 20 g/L,the plated coatings possessed the largest passivation potential range and the smallest corrosion current density in their anodic polarization curves,therefore,corrosion resistance of the coatings got the best.