在三价铬Cl^--SO_4^(2-)体系中电沉积厚镀层的研究

Thick Chromium Electrodeposition From Bath Containing Cl\+-\|SO\+\{2-\}\-4 and Urea Mixture

研究了在新型尿素氯化物硫酸盐混合物三价铬溶液中电镀铬的工艺条件对镀层的影响，详细考察了电流密度、ｐＨ值、络合剂浓度、恒电流／恒电位方式对电流效率和镀层外观质量的影响。结果表明：ｐＨ值在１．９～２．３之间、电流密度在７～１１Ａ／ｄｍ２范围内、络合剂浓度为２ｍｏｌ／Ｌ时获得的镀层能达到较大厚度和较高的电流效率，镀层光亮致密。在此工艺条件下，可获得３０～４０μｍ的镀层。提出了三价铬电化学聚合的新假设。

Abstract)The technological conditions of thick chromium electroplating from the bath containing Cr\+\{3+\}, Cl\+-\|SO\+\{2-\}\-4 and a new urea mixture were investigated. The effect of acidity, current density, concentration of complex and the mode of constant potential/constant current on current efficiency were also studied. Under the optimium operation conditions pH 1.9￣2.3, \%D\%\-K=7￣11 \{A/dm\+\{2\}\}, urea concentration 2 mol/L, 30￣40 m bright chromium deposits can be obtained. A possible factor hindering sustained deposition was regarded as electrochemical polymerization of Cr\+\{3+\}.