电解活化-冲击镀镍前处理提高316L不锈钢表面电镀Pd-Ni合金膜层的耐蚀性能

Improvement of Corrosion Resistance of Electroplated Pd-Ni Alloy Film on 316L Stainless Steel by Anodic Electrolytic Activation-Nickel Strike Pretreatment

目的提高Pd-Ni合金膜层与不锈钢基体间的结合力,减小膜层孔隙率,改善不锈钢电镀Pd-Ni合金膜层的耐蚀性。方法分别采用阳极电解活化-冲击镀镍前处理工艺和阴极活化前处理工艺后在316L不锈钢表面制备Pd-Ni合金膜层,对比研究两种方法得到膜层的微观形貌、显微硬度、孔隙率,结合力等物理性能,通过腐蚀失重实验、极化曲线测试和扫描电子显微镜等系统研究两种膜层试样的耐腐蚀性和耐冲刷腐蚀性能。结果与阴极活化后制备的Pd-Ni膜层相比,阳极电解活化-冲击镀镍处理后制备的Pd-Ni膜层(简称Ni/Pd-Ni膜层)具有相同的微观形貌和元素组成。镀镍1 min的Ni/Pd-Ni膜层的硬度为373.8HV,孔隙率为1.33个/cm2,结合力为12.94 MPa;而Pd-Ni膜层的硬度为351.4HV,孔隙率为3.33个cm2,结合力为1.31 MPa。在温度为80℃的20%硫酸或20%硫酸+0.001 mol/L的Cl–溶液中,Ni/Pd-Ni膜层试样的腐蚀速率约为Pd-Ni膜层试样的1/3。在80℃,20%硫酸+100 g/L Si O2颗粒,1200 r/m搅拌的冲刷腐蚀溶液中,Ni/Pd-Ni膜层的寿命大约是Pd-Ni膜层寿命的4倍。结论电解活化-冲击镀镍前处理工艺能够改善Pd-Ni膜层的物理性能,尤其是结合力得到了显著提高。Ni/Pd-Ni膜层试样的耐蚀性和耐冲刷腐蚀性能均优于Pd-Ni镀层试样。

Objective To improve the adhesion strength between the film and stainless steel substrate, decrease porosity of the film, and enhance the corrosion resistance of electroplated Pd-Ni alloy film on stainless steel. Methods Pd-Ni film was prepared on 316 L stainless steel according to processes of anodic electrolytic activation-nickel strike and cathodic activation pre-treatment. Physical properties such as surface morphology, micro-hardness, porosity and adhesive strength of the films prepared by the two processes were comparatively studied, and corrosion resistance and erosion-corrosion resistance of the Pd-Ni films by two pretreatments were measured by corrosion weight loss test, polarization measurement and scanning electron microscope. Results Compared with the Pd-Ni alloy film prepared after cathodic activation（Pd-Ni film）, the Pd-Ni alloy film prepared after anodic electrolytic activation-nickel strike（shorted as Ni/Pd-Ni film） had the same surface morphology and elementary composition. The micro-hardness of the Ni/Pd-Ni film was 373.8HV, porosity was 1.33 cm–2, and adhesive strength was 12.94 MPa; while the micro-hardness of the Pd-Ni film was 351.4HV, porosity was 3.33 cm–2, and adhesive strength was 1.31 MPa. The corrosion rate of the samples plated with Ni/Pd-Ni film in both 20 wt.% H_2SO_4 and 20 wt.% H_2SO_4 ＋ 0.001 mol·L–1 Cl– solutions at 80 ℃ was about 1/3 that of the sample plated with Pd-Ni film. At 80 ℃, 20 wt.% H_2SO_4 ＋ 100 g·L–1 SiO_2 particles with 1200 r/min stirring, the lifetime of Ni/Pd-Ni film was about 4 times that of the Pd-Ni film. Conclusion Physical properties of the Pd-Ni film can be improved by anodic electrolytic activation-nickel strike pretreatment process, especially the adhesion strength increases by almost an order of magnitude. The corrosion resistance and erosion-corrosion resistance of the Ni/Pd-Ni film plated samples are obviously increased.