Layer-by-layer analysis of hot-dip zinc coating by anodic dissolution in acetate bath

To analyze the distribution of the alloying elements in hot-dip zinc coatings, a layer-by-layer electrochemical dissolution method was studied by using an acetate bath. The research was performed by means of galvanostatic anodic polarization, chemical analysis and metallographic analysis. A suitable...

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Bibliographic Details
Published in:Surface & coatings technology 2012-08, Vol.206 (24), p.5023-5027
Main Authors: Bellezze, T., Saltykov, S., Roventi, G., Malavolta, M., Fratesi, R.
Format: Article
Language:English
Subjects:
Acetate bath
Alloying elements
Anodic stripping
Galvanostatic polarization
Hot-dip zinc coating
Layer-by-layer analysis
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Summary:To analyze the distribution of the alloying elements in hot-dip zinc coatings, a layer-by-layer electrochemical dissolution method was studied by using an acetate bath. The research was performed by means of galvanostatic anodic polarization, chemical analysis and metallographic analysis. A suitable cell was constructed to perform this study. Results show that the electrochemical dissolution of η-phase is uniform, while δ-phase dissolves partially together ζ-phase, due to the formation of cracks in the coating during polarization. Faraday's law was used to demonstrate that galvanostatic dissolution of hot-dip zinc coating at 12.7mAcm−2 proceeds by electrochemical mechanism without chemical dissolution; on the contrary, the occurrence of this second process was found at lower stripping current density. During polarization, the formation of a black film which interferes with the subsequent dissolution process was found. Mechanical removal of black film from electrode surface leads to the decrease of cracks formation and to a more uniform layer-by-layer dissolution. A method to obtain layer-by-layer analysis of the alloying elements of a hot-dip zinc coating, as a function of its thickness, by controlled electrochemical dissolution is suggested. ► We studied a method for layer-by-layer anodic dissolution of hot-dip zinc coatings. ► We constructed a suitable cell to perform this study. ► Results show that the dissolution of η-phase is uniform. ► δ-phase dissolves partially together ζ-phase. ► A black film interferes with the subsequent dissolution processes.
ISSN:0257-8972
1879-3347
DOI:10.1016/j.surfcoat.2012.04.008