无氰电镀镉—钛合金工艺及电沉积行为研究

发布时间：2018-07-08 10:23

  本文选题：无氰电镀镉-钛 + 钛含量　； 参考：《南昌航空大学》2017年硕士论文

【摘要】：无氰电镀镉-钛合金镀层可作为高强度钢的防护层,该镀层中微量的钛(0.1-0.7%)对镀层的氢脆性能和耐蚀性能有较大的影响,但在实际生产中仍存在镀层中钛含量难以控制,镀液不够稳定易水解等技术难题,阻碍了该项技术的推广应用。本文以中性铵盐镀镉液为基础镀液,加入自制的氯氧钛,采用电沉积法制备了镉-钛合金镀层,通过极化曲线法、X射线光电子能谱(XPS)等测试方法探索了镉-钛合金镀层的电沉积行为;利用扫描电镜(SEM)、X射线衍射仪(XRD)观察了镀层微观形貌和晶面取向,采用单因素实验研究了工艺参数对镀层钛含量的影响;利用“陈化”实验和“连续镀”实验研究了镀液的稳定性,主要研究结果如下:1.无氰电镀镉-钛合金镀液中的钛酰离子在阴极表面未发生电化学反应,而是在阴极界面处与OH-反应生成TiO2和少量的Ti_2O_3,夹杂于镉镀层中,其沉积过程推测为:TiO~(2+)+OH-→ TiO_2+H~+TiO~(2+)+H→ TiO~++H~+2TiO~++2OH-→ Ti_2O_3+H_2O镀液中钛盐的引入增大了工作电流密度区的阴极极化,使镉的形核过电位变大,镀层晶粒变细。2.自制主盐氯氧钛时,钛与盐酸的比例控制为1:4(g/ml),中性铵盐镀镉液中引入该自制的氯氧钛(钛含量)为4-5 g/L,且镀液中钛与镉的比例为1:3,施镀时电流密度控制为2-3 A/dm~2时,获取10μm镉-钛合金镀层为稻黄色,钛含量达0.4%左右,且该镀液可长期稳定使用。3.无氰镀纯镉层表面为暗灰色,结晶粗糙,主要取向为(101)、(002)面,沉积类型为倾斜型镀层,而镀液中引入自制的氯氧钛所获取的镉-钛合金镀层(钛含量约为0.5%)表面呈稻黄色,结晶细致,在(101)、(100)、(110)面为主要取向,沉积类型为垂直型镀层,钛的引入改变了镀层的择优取向和沉积类型,有利于氢气的释放,降低了氢脆的可能性。另外镉-钛合金镀层的自腐蚀电位为-0.825 V,自腐蚀电流密度为1.765×10-2 A/dm~2,比纯镉镀层的自腐蚀电位更正,自腐蚀电流密度更小,镀层的耐蚀性增强。4.“陈化”实验和“连续镀”实验研究表明:新配制的镀液pH值为5.99和7.05时,镀液稳定常数分别为0.886和0.873,18 d后镀液变浑浊,而pH值为6.7时,稳定常数为0.946,该镉-钛合金镀液在10-60℃室内长期存放时,未产生沉淀,但温度高于60℃时,镀液开始浑浊,产生白色沉淀,沉淀产物主要是Ti(OH)_4、TiO_2、H_2Ti_2O_(11)·3H_2O、NH_4Cl;新配制的25 L镀液连续施镀过程中,施镀至16 d时,通电量为2.07×10~6 C,镀层钛含量达到峰值,至28 d后,通电量为3.63×10~6C,镀层钛含量低于0.1%,镀液中络合剂消耗较快,需重新分析补充镀液的成分,确保其能长期稳定生产。
[Abstract]:The non-cyanide cadmium titanium alloy coating can be used as a protective layer for high strength steel. The trace amount of titanium (0.1-0.7%) in the coating has a great influence on the hydrogen embrittlement and corrosion resistance of the coating, but it is still difficult to control the titanium content in the coating in actual production. The solution is not stable and easy to hydrolyze, which hinders the popularization and application of the technology. In this paper, cadmium-titanium alloy coating was prepared by electrodeposition with neutral ammonium salt cadmium plating solution and adding self-made titanium oxychloride. The electrodeposition behavior of cadmium-titanium alloy coating was investigated by means of X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effect of technological parameters on titanium content of the coating was studied by single factor experiment, and the stability of plating solution was studied by "aging" experiment and "continuous plating" experiment. The main results were as follows: 1. There was no electrochemical reaction between Ti ~ (2 +) ions and OH- on the cathode surface in the cadmium-titanium alloy plating bath without cyanide. Instead, TIO _ 2 and a small amount of Ti _ 2O _ 3 were formed at the cathode interface to form a small amount of Ti _ 2O _ 3, which was mixed with cadmium coating. The deposition process of TiO2OH- TiO- TiO- TiO- + TiO- TiO- TiO- Ti2O2Ti2O3H- Ti2O3H- Ti2O3H- Ti2O2Ti2O3H- Ti2O2Ti2O3H- Ti2O2Ti2O3H- Ti2O-Ti2O2Ti2O3H- Ti2O-Ti2O-TiO- TiO- TiO- TiO- TiO@@ The ratio of titanium to hydrochloric acid was controlled at 1:4 (g/ml) when the main salt was made by ourselves. The titanium oxychloride (titanium content) was introduced into the neutral ammonium salt cadmium plating solution was 4-5 g / L, and the ratio of titanium to cadmium in the bath was 1: 3, and the current density was 2-3 Ar / dm2 when the plating was applied. The 10 渭 m cadmium-titanium alloy coating is rice-yellow, the titanium content is about 0.4%, and the bath can be used steadily for a long time. The surface of pure cadmium without cyanide plating is dark gray, crystal rough, and the main orientation is (101), (002) surface. The deposit type is inclined type. The surface of cadmium titanium alloy coating (about 0.5% titanium content) obtained by introducing self-made titanium oxychloride into the bath is rice yellow. The crystal is fine, the main orientation is on the (101), (100), (110) surface, and the type of deposition is vertical. The introduction of titanium changes the preferred orientation and deposition type of the coating, which is favorable to the release of hydrogen and reduces the possibility of hydrogen embrittlement. In addition, the self-corrosion potential of the coating is -0.825 V, the self-corrosion current density is 1.765 脳 10 ~ (-2) A / D ~ (-2), the self-corrosion current density is smaller than that of the pure cadmium coating, and the corrosion resistance of the coating is enhanced by .4.The results show that the corrosion resistance of the coating is better than that of the pure cadmium coating. The results of "aging" experiment and "continuous plating" experiment show that when the pH value of the newly prepared bath is 5.99 and 7.05, the bath stability constant is 0.886 and 0.873ng respectively, and the bath becomes turbid after 18 days, while the pH value is 6.7. The stability constant was 0.946. When the cadmium titanium alloy plating bath was stored in room for a long time at 10-60 鈩，

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