三价铬电沉积机理研究及镀层表征
Deposition mechanism and coating characterization for the trivalent chromium plating process
芦鑫 1冯长杰 1李杰 1王赫男 1辛丽 2王福会3
作者信息
- 1. 沈阳航空航天大学 材料科学与工程学院,辽宁 沈阳 110136
- 2. 中国科学院金属研究所 腐蚀与防护实验室,辽宁 沈阳 110016
- 3. 东北大学 材料科学与工程学院,辽宁 沈阳 110819
- 折叠
摘要
在硫酸盐三价铬电沉积体系中,通过赫尔槽实验对不同络合剂含量进行了筛选,得到络合剂最佳含量配比为甲酸铵80 g/L、草酸铵20 g/L以及尿素30 g/L,最佳电流密度范围为5.11 A/dm2～20.68 A/dm2;通过循环伏安曲线和阴极极化曲线分析三价铬电沉积机理,发现三价铬的沉积过程分两步进行:第一步为Cr3++e→Cr2+,过程不可逆;第二步为Cr2++2e→Cr,可逆;草酸铵会增大阴极极化,甲酸铵和尿素会降低阴极极化;电沉积20 min得到的铬镀层,XPS分析表面镀层由单质Cr、Cr2O3及Cr(OH)3构成;微观结构观测发现,随着电沉积时间增加,镀层由表面平整形貌逐渐转变为瘤状结构形貌;镀层呈现明显的(110)择优取向;电化学研究表明,相比20 min铬镀层,5 min铬镀层的耐蚀性较好,腐蚀电位由-0.6377 V提高至-0.5633 V,腐蚀电流由6.1030×10-6 A/cm2提高至5.4031×10-6 A/cm2.
Abstract
Different complexing agent contents were screened through Hull Cell experiments in the sulfate trivalent chromium electrodeposition system,and the best content ratio of complexing agent was obtained.The optimum content ratio was 80 g/L ammonium formate,20 g/L ammonium oxalate and 30 g/L urea.The optimal current density range was 5.11 A/dm2 to 20.68 A/dm2.Cyclic voltammetry and steady polarization were used to study the mechanism of Cr(Ⅲ)electrodeposition in this system,the trivalent chromium reduced through two steps.The first step was Cr3++e→Cr2+,which it was irrevers-ible,while the second step was Cr2++2e→Cr,which it was quasi-reversible.Ammonium oxalate increased cathodic polarization,while ammonium formate and urea reduced cathodic polarization.The chromium coating obtained by electrodeposited for 20 min was composed of Cr,Cr2O3 and Cr(OH)3 according to XPS analysis.The microstructure observation showed that with the increase of electrodepo-sition time,the morphology of the coating gradually changed from a flat surface to a nodular tructure.The plating layer exhibited a clear(110)preferred orientation.Electrochemical studies had shown that compared with 20 min chromium coating,5 min chromium coating had better corrosion resistance,the corrosion potential increases from-0.6377 V to-0.5633 V,and the corrosion current increases from 6.1030×10-6 A/cm2 increased to 5.4031×10-6 A/cm2.
关键词
三价铬电镀/络合剂/电沉积机理/微观结果/耐蚀性能Key words
trivalent chromium plating/complexing agent/electrodeposition mechanism/microscopic results/corrosion resistance properties引用本文复制引用
基金项目
辽宁省"兴辽英才计划"项目资助(XLYC2002031)
沈阳航空航天大学引进人才启动基金资助(19YB05)
出版年
2024
NETL
NSTL
万方数据