材料期刊网

目的 提高金属材料在海洋环境中的耐腐蚀性和使用寿命.方法 采用碱式化学镀方法 在Q235碳钢表面施镀Ni-P镀层和Ni-Zn-P合金镀层,镀液配方NiSO4·6H2 O 20~25 g/L,C6 H5 O7 Na3·2H2 O 50~70 g/L,NH4Cl 25~30 g/L,NaH2PO2·H2O 15~25 g/L.制备Ni-Zn-P合金镀层时,在以上配方中加入0.4~0.8 g/L ZnSO4·7H2 O.采用金相显微镜和扫描电子显微镜(SEM)观察镀层在人工模拟海水中腐蚀前后的组织形貌,用能谱分析仪(EDS)分析镀层腐蚀前后表面成分.结果 Ni-P镀层和Ni-Zn-P合金镀层中的P质量分数分别为11.26%和9.97%.从P含量和镀层组织形貌,可以确定得到的两种镀层是连续致密的非晶镀层.Ni-Zn-P合金镀层比Ni-P镀层的胞状组织更加均匀平滑,胞与胞的边界结合更加连续致密.在人工模拟海水中腐蚀144 h后,Ni-P镀层出现明显的点蚀坑,Ni-Zn-P合金镀层仍然连续完整.Ni-Zn-P合金镀层腐蚀后,Zn含量明显下降,并出现少量的Fe和O,表明合金镀层腐蚀过程是Zn优先被腐蚀,然后镀层逐渐被腐蚀破坏,最后基体发生腐蚀.Ni-Zn-P合金镀层的腐蚀速率明显低于Ni-P镀层的.结论 Ni-Zn-P合金镀层的胞状组织比Ni-P镀层的更加均匀平滑,胞与胞的边界结合更加连续致密,Ni-Zn-P合金镀层腐蚀速率明显低于Ni-P镀层.

Objective To improve the service life and corrosion resistance of metal materials in the marine environment. Methods The Ni-P coating and Ni-Zn-P alloy coatings were prepared on Q235 steel by alkaline electroless plating technique. The bath formula was:NiSO4 ·6H2 O 20~25 g/L,C6 H5 O7 Na3 ·2H2 O 50~70 g/L, NH4 Cl 25~30 g/L, NaH2 PO2 ·H2 O 15~25 g/L. Ni-Zn-P alloy coating was prepared by adding 0. 4~0. 8 g/L of ZnSO4 ·7H2 O into the above formula. The surface morphology of coatings before and after corrosion in artificial simulated seawater was observed by optical microscope and SEM. The surface com-position of coatings before and after corrosion was analyzed by EDS. Results The P contents of Ni-P plating and Ni-Zn-P alloy coat-ing were 11. 26 wt% and 9. 97 wt%, respectively. From the P content and coating microstructure, it ccould be determined that the two coatings obtained were continuous dense amorphous coatings. The Ni-Zn-P alloy coating was more uniform and smooth than the Ni-P coating, and the cell boundary was more continuous and denser. After 144 h corrosion in artificial simulated seawater, Ni-P coating showed obvious pitting, while the Ni-Zn-P alloy coating was still intact without damage and localized corrosion. After corro-sion, the content of Zn decreased obviously and a small amount of Fe and O appeared in the Ni-Zn-P alloy coating, indicating that Zn was first corroded in the corrosion process of the alloy coating, then the coating was gradually corroded, and finally, the sub-strate was corroded. The corrosion rate of Ni-Zn-P alloy coating was significantly lower than that of Ni-P coating. Conclusion The Ni-Zn-P alloy coating was more uniform and smooth than the Ni-P coating, and the cell boundary was more continuous and denser. The corrosion rate of Ni-Zn-P alloy coating was significantly lower than that of Ni-P coating.