| HUANG Yong,DU Nan,SHEN Zong-yao,WANG Shuai-xing.Cyanide Free Cadmium Plating Process for Hydantoin System[J],48(2):239-245 |
| Cyanide Free Cadmium Plating Process for Hydantoin System |
| Received:August 01, 2018 Revised:February 20, 2019 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2019.02.034 |
| KeyWord:cyanide free cadmium maine cadmium plating additive sealant corrosion resistances |
| Author | Institution |
| HUANG Yong |
School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang , China |
| DU Nan |
School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang , China |
| SHEN Zong-yao |
School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang , China |
| WANG Shuai-xing |
School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang , China |
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| Abstract: |
| The work aims to develop a new cyanide free cadmium plating process to replace the traditional cyanide cadmium plating. The formulation of cyanide-free cadmium plating process was obtained with hydantoin and citric acid as the main material and complexing agents as auxiliary materials by selecting brightener and surface active agent. The processing parameters like pH value, current density and temperature were optimized. The dispersing ability and deep plating ability of the bath were tested according to the prescribed method. The micro-morphology of the coating was observed by SEM and 3D microscope. The polarization and film-forming mechanism were discussed by polarization curve and cyclic voltammetry. The corrosion resistance of the coating was tested by Tarfield curve and drop test. Cadmium electrodeposition was carried out through the mechanism of nucleation/growth. The synergistic effect of double complexing agents on cyanide-free cadmium plating in hydantoin system was obvious and the polarization ability of the plating solution was strong. Compared with cyanide cadmium plating, the current efficiency of the process was increased by 20%, the deposition rate was increased by 30%, and the dispersing ability was over 89%. The deep plating ability of the bath and the adhesion of the coating were qualified. The surface of the coating was bright and meticulous, and the iridescent color of the passive film was obvious. The corrosion resistance of cyanide-free cadmium plating layer was better than that of cyanide cadmium plating layer. Compared with cyanide cadmium plating passivation layer, after passivation and closure, the corrosion current density decreased to 1/15 before, and the corrosion resistance was significantly improved. The formulation and technological conditions are: cadmium sulfate of 30~50 g/L, sodium sulfate of 60~100 g/L, hydantoin of 60~70 g/L, citric acid of 20~40 g/L, brightener of 1~3 g/L, surfactant of 1~3 g/L, pH=5~6 and temperature of 15~35 ℃. The plating bath has superior properties and can completely replace the cyanide cadmium plating process to protect aircraft and aeroengine steel structures in China. |
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