摘要
[目的]三价铬电沉积过程中伴随的剧烈析氢反应导致局部pH升高,是镀速急剧下降、镀层难以增厚及镀层性能恶化的主要原因。[方法]采用甲酸钠、草酸钠和尿素为氯化物体系三价铬电镀的配位剂,以在150 mA/cm^(2)电流密度下电沉积10 min的沉积速率为响应因子,采用响应曲面法优化了镀液配方,建立了氯化物体系三价铬电沉积速率的多项式模型方程。通过单因素实验研究了添加剂、pH、温度、电流密度和沉积时间对沉积速率、镀液深镀能力和镀层耐蚀性的影响。[结果]三价铬电沉积的最佳配方和工艺条件为:三氯化铬0.6 mol/L,甲酸钠0.8 mol/L,草酸钠0.2 mol/L,尿素0.3 mol/L,pH 1.8,温度30℃,电流密度150 mA/cm^(2),时间30 min。在该条件下所得Cr镀层为非晶态结构,厚度在12μm以上,耐蚀性良好。[结论]选用合适的配位剂抑制电沉积过程中铬的羟桥化反应,是维持较高镀速和改善镀层性能的有效手段。
[Introduction]The drastic hydrogen evolution reaction accompanies with the electrodeposition of chromium leads to the rise of local pH,which is the primary cause of dramatic decrease in deposition rate,difficulty in coating thickening,and deterioration of coating properties.[Method]Sodium formate,sodium oxalate,and urea were selected as the complexing agents for electrodeposition of trivalent chromium.The bath composition was optimized by response surface method using the deposition rate at 150 mA/cm^(2) within 10 min as the response,and a polynomial equation for predicting the deposition rate of trivalent chromium in a chloride-based bath was established.The effects of additive,pH,temperature,current density,and electrodeposition time on the deposition rate,throwing power of the bath,and corrosion resistance of Cr coating were studied by single-factor experiments.[Result]The bath composition and process conditions were optimized as follows:chromium trichloride 0.6 mol/L,sodium formate 0.8 mol/L,sodium oxalate 0.2 mol/L,urea 0.3 mol/L,pH 1.8,temperature 30℃,current density 150 mA/cm^(2),and time 30 min.The Cr coating electrodeposited under the optimal conditions was amorphous with a thickness higher than 12μm and good corrosion resistance.[Conclusion]It is an effective way to maintain a high deposition rate and improve the coating properties by selecting appropriate chelating agents to inhibit the hydroxylation reaction of chromium during electrodeposition.
作者
夏爽
王彬
王议
刘中清
XIA Shuang;WANG Bin;WANG Yi;LIU Zhongqing(School of Chemical Engineering,Sichuan University,Chengdu 610065,China;School of Chemical Engineering,Sichuan University of Science&Engineering,Zigong 643000,China)
出处
《电镀与涂饰》
CAS
北大核心
2024年第3期10-21,共12页
Electroplating & Finishing
关键词
三价铬
电沉积
氯化物体系
组合配位剂
响应曲面法
非晶态
trivalent chromium
electrodeposition
chloride-based bath
composite complexing agent
response surface methodology
amorphous phase
