【作者】 朱学松；

【导师】 高俊杰； 安成强；

【作者基本信息】 沈阳理工大学 ， 应用化学， 2009， 硕士

【摘要】 硫酸盐镀锌液具有成分简单、电流效率高（接近100%）、沉积速度快等优点,常用于高速电镀。镀锌层在长期贮藏过程中表面出现黑色或茶褐色膜层的现象,称之为黑变。这种黑色膜层严重影响了钢板的外观质量。为了降低镀锌层的黑变影响并探讨镀锌层黑变的产生机理,本文对高速电镀锌工艺进行了优化,并通过加速腐蚀试验、金相显微观察、SEM微观形貌观察及X射线衍射等方法分别研究了静态和动态条件下镀液中杂质离子对镀层微观形貌,镀层结晶取向度以及镀层耐黑变性能的影响,同时研究了环境因素对镀层耐黑变性能的影响,并提出了缓解黑变的措施。试验了在静态下,电流密度为15A/dm2时,镀层的耐黑变性能最强;杂质对镀层外观质量、微观形貌和耐黑变性能有负面影响,镀液对杂质的容忍范围为:铜离子0¹.0mg/L;镍离子0⁴00mg/L;铁离子0⁸00mg/L;铝离子对镀层的影响不大。在动态下,镀层的结晶大小比静态时的要小很多,耐黑变性能也增强了。随着镀液流速和电流密度的增大,降低了浓差极化同时增大电化学极化,镀层结晶变得更加细致,耐黑变性能有所提高,晶面（002）、（004）择优取向度逐渐减小,其他晶面的择优取向度逐渐增大;其他工艺参数对镀层耐黑变性能影响相对较小,得出最佳工艺条件为:电流密度50A/dm²、流速大于3.2m/s、Zn²⁺浓度120g/L、温度40℃、pH为2.2。相对静态下,镀液对杂质的容忍范围变宽。另外,在镀锌之前闪镀一层镍能够增强镀锌层耐黑变性能,并且当闪镀镍量为100mg/m2时,晶面（002）、（004）择优取向度最小,耐黑变性能最强,涂防锈油也具有较好的耐黑变作用。更多还原

【Abstract】 Zinc sulphate electrolytes are used for continuous high speed plating on account of their simple ingredient, high current efficiency and quick deposition rate. When galvanized sheet steel is stored for a long time, a kind of black or brown film is formed on the surface. The phenomenon is went by the name of black patina. The black film seriously affects the appearance of surface. In this paper, high speed electrogalvanizing process is optimized and the influence of metallic impurities on the performances of coating, including black patina resistance, micromorphology and degree of orientation of crystal face, is researched by humid-hot-test, microscopicexamination and XRD analyses in static state and dynamic state respectively. It is to decrease degree of black patina and investigate the formation mechanism of black patina film. The influence of environmental factors on coating is researched and the measures which relieve black patina are proposed.In static state, black patina resistance of coating is the best when current density is 15A/dm2. impurities affect the performances of coating, including appearance of surface, black patina resistance and micromorphology, negatively. The tolerant scopes of electrolyte to impurities are as follows: copper ion 0~1.0mg/L; nickel ion 0~400mg/L; iron ion 0~800mg/L; influence of aluminium ion on zinc electrowinning is neglectable.When electrolyte is flowing, the crystal size of coating is smaller than coating’s in static state and black patina resistance is enhanced. Concentration polarization is decreasing and electrochemical polarization is increasing with increasing flow rate of solution and current density, at the same time, crystal size become smaller and black patina resistance is enhanced; degree of orientation of crystal face (002), (004) is decreased and other’s is increased gradually. The effect of other technological parameters on coating is less relatively. The best process condition is: current density (50A/dm2), flow rate (>3.2m/s), concentration of zinc ion (120g/L), temperature (40℃), pH(2.2). The tolerant scopes of electrolyte to impurities are wider than the scopes in static state.Besides, nickel electroplating can enhance black patina resistance before zinc electrowinning, and when the quantity of nickel electroplating is 100mg/m2, degree of orientation of crystal face (002), (004) is least, black patina resistance is best. Painting pickling oil can also enhance black patina resistance.更多还原