阴极电流密度对超高强钢锌镍镀层腐蚀及氢脆性能的影响

The Influence of Cathodic Current Density on Corrosion Behavior and Hydrogen Embrittlement of Ultrahigh Strength Steel

碱性电镀锌镍因生产过程更环保、镀层耐蚀性好等优点,已成为代镉技术的首选。但是,由于氢脆等原因,暂未应用于超高强钢A100的表面防护。采用一种碱性镀液配方,在不同阴极电流密度下对超高强钢A100表面进行电镀及钝化,同时对钝化后的镀层进行了物相、微观形貌、电化学性能、盐雾、氢脆等组织及性能进行表征。结果表明:在阴极电流密度为2—4 A∙dm^(−2)范围内,可得到单一γ相镀层,并且镍含量在12%—13%左右;当阴极电流密度为2 A∙dm^(−2)时,析氢反应进行得比高电流密度时剧烈,电镀效率较低,需要更长的电镀时间才能得到与阴极电流密度为3—4 A∙dm^(−2)时耐蚀性相近的镀层。本镀液配方制备的镀层氢脆性能好,带有镀层的试棒均通过了200 h缺口拉伸测试,且在3—4 A∙dm^(−2)阴极电流密度电镀时渗氢电流也保持在了一个较低水平。

Because of the superior corrosion resistance of the Zn-Ni layers and their ecologically benign manufacture,alkaline Zn-Ni electroplating has supplanted cadmium electroplating as the favored method.Nevertheless,it has not been used to the surface protection of ultra-high-strength steel A100 yet because of hydrogen embrittlement.Here,an alkaline plating solution was used to electroplate and passivate the ultra-high strength steel A100 at varying cathode current densities.The layers'microstructures,electrochemical characteristics,resistance to salt spray,and hydrogen embrittlement were all examined.The findings indicate that a singleγphase would form under a cathode current density range of 2—4 A∙dm^(−2),and that the electroplated layer would contain 12—13 wt%nickel.Lower electroplating efficiency is the result of a more powerful hydrogen evolution process at a cathode current density of 2 A∙dm^(−2),as opposed to higher current densities.Furthermore,compared to electroplating under 3—4 A∙dm^(−2),it takes longer to generate an electroplated layer with respectable corrosion resistance under 2 A∙dm^(−2).The A100 steel has strong resistance against hydrogen embrittlement with the alkaline plating solution.The test bars with electroplated layers can pass the 200-hour notch-tensile tests,and they also maintain a comparatively low hydrogen permeation current under 3—4 A∙dm^(−2).