硫酸盐体系三价铬电镀黑铬的工艺

Technology for Black Chromium Electroplating in Trivalent Chromium Sulfate Electrolyte

为了寻找更环保、更稳定的三价铬电镀黑铬工艺,采用Hull Cell和小槽试验优选了硫酸盐体系三价黑铬电镀液中发黑剂、辅助发黑剂的种类及用量,并对镀液和镀层性能进行了测试。结果表明:最优三价铬电镀黑铬工艺为35 g/L碱式硫酸铬,30 mL/L配位剂,150 g/L硫酸钠,80 g/L硫酸钾,70 g/L硼酸,3 mL/LBNW-1润湿剂,2～4 g/L半胱氨酸,1～2 g/L硫氰酸钾,pH值3.4～3.8,温度50～60℃,阴极电流密度5～10A/dm2;以该工艺进行三价铬电镀黑铬,镀液稳定性好、分散能力强,电流密度范围宽,可达2.5～15.0 A/dm2;该工艺制备的黑铬镀层主要成分为Cr,S以及少量有机物;镀层黑度好,耐蚀性好,与基体结合良好。

Hull cell tests and small-cell simulated electroplating tests were conducted in relation to the selection of the blackening agents and auxiliary blackening agents for black trivalent chromium electroplating in sulfate electrolyte. The properties of the electroplating bath and as-plated black Cr coating were analyzed. Results indicated that the optimal bath for trivalent black Cr electroplating consisted of 35 g/L basic chromium sulfate,30 mL/L coordination agent,150 g/L sodium sulfate,80 g/L potassium sulfate,70 g/L boric acid,3 mL/L BNW-1 wetting agent,2 ～ 4 g/L cysteine,and 1 ～ 2 g/L potassium thiocyanate. In the meantime,the optimized electroplating parameters were determined to be pH value of 3. 4 ～ 3. 8,temperature of 50 ～ 60 ℃ ,and cathodic current density of 5 ～ 10 A/dm 2 . The electroplating bath with the optimal composition for trivalent black Cr electroplating had good stability and a wide range of current density (2. 5 ～ 15. 0 A/dm 2) . As-plated black Cr coating obtained under the optimized electroplating condition consisted of Cr and S as the major ingredients and a small amount of organic compounds as the minor ingredients,and it possessed good corrosion resistance as well as good adhesion to substrate.