Co-Cu合金电镀工艺研究及其后续尖晶石涂层的制备探索

Preparation of Cu-Co Spinel Coatings on 430 Stainless Steel by Electro-deposition and Post-oxidation

以柠檬酸盐为络合剂在铁素体不锈钢表面电镀Cu-Co合金,重点研究镀液pH值和沉积电位对电镀过程和镀层微观结构的影响。结果表明,在pH值为4~6镀液中Cu^(2+)与柠檬酸盐几乎完全络合,而Co^(2+)则以简单离子存在,络合Cu^(2+)与简单Co^(2+)的沉积电位相近,可实现Cu-Co合金共沉积。当pH值为4时镀层成分稳定性较佳。在pH值为4、沉积电位为-0.9^-1.1 VSCE时,随着电位值的增大镀层中Co/Cu(原子分数)相应增加。当沉积电位为-1 VSCE时,镀层中Co/Cu约为2。在800℃预氧化2 h后镀层转变为均匀致密、与基体之间结合良好的Cu-Co尖晶石涂层。涂层由三层结构组成:外层为一薄层Cu O;中间为一层较厚的Cu_(0.92)Co_(2.08)O_4尖晶石;内层为连续的Co_3O_4。

Cu-Co alloy coatings can be prepared on ferritic stainless steel by electro-deposition in Co- and Cu-sulfate bath with citrate as complex agent. The effect of pH value of the electrolyte and the electrodeposition potential on the deposition process and microstructure of the coatings was investigat- ed. In a range of pH value 4-6, Cu2＋ can coordinate with citrate almost completely, while Co2. remains to exist as simple ions. Since the deposition potential of the complexing Cu2＋ is similar to that of the simple Co2＋, co-deposition of Cu-Co alloy can be realized in the electrolyte with pH value within the above range. Coatings with a more stable chemical composition are obtained at pH value of 4. At pH=4 and deposition potential of-0.9--1.1 VscE, the Co/Cu （atomic fraction） increases with the increasing deposition potential. An optimal composition with Co/Cu of about 2 is acquired at pH=4 and deposition potential of-1 VscE. Af- ter oxidation at 800℃ in air for 2 h, the Co-Cu alloy coating was converted into an adherent and compact three-layered scale composed of an external thinner CuO layer, a middle thicker Cu092Co20804 layer and an inner Co2O, layer.