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

摘要:

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。

Abstract:

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 single γ phase 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.