The effect of the chemical composition of intermetallic phases on the corrosion of thermal diffusion zinc coatings

• Published in: Surface & coatings technology Vol. 372; pp. 166 - 172
• Main Authors: Biryukov, А.I., Galin, R.G., Zakharyevich, D.А., Wassilkowska, A.V., Batmanova, Т.V.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 25-08-2019; Elsevier BV
• Subjects: Chemical composition; Composition effects; Corrosion; Corrosion effects; Corrosion products; Corrosion rate; Delta phase (crystals); Dependence; Diffusion coatings; Fe-Zn intermetallics; Intermetallic phases; Iron; Organic chemistry; Sherardizing; Simonkolleite; Thermal diffusion; Thermal diffusion galvanizing; Zinc coatings; Sherardizing; Simonkolleite; Corrosion; Fe-Zn intermetallics; Thermal diffusion galvanizing
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2019.05.029

The corrosion behavior of thermal diffusion zinc coatings of various chemical and phase compositions in chloride-containing media was studied. The corrosion rate of the δ phase, FeZn7–10, depends non-monotonically on the composition of the surface, with minimum approximately in the middle of homogeneity range of δ phase. The main crystalline product of corrosion of coatings in chloride-containing media is simonkolleite, Zn5(OH)8Cl2·H2O, doped with iron. The observed behavior can be explained by the combined effect of small amounts of iron in the coating and the dependence of the structural parameters of the δ phase on the composition.
•Thermal diffusion zinc coatings containing intermetallic Fe–Zn phases were formed from Zn powders with nanostructured ZnO.•An increase in the galvanizing time leads to an increase in the zinc content in the surface layers of the coating.•The dependence of the corrosion rate of investigated coatings with only δ-phase, on the Zn content is non-monotonic.•Minimum of the corrosion rate observed in coatings with Zn content 90 wt.%.•Simonkolleite is product of corrosion in chloride-containing media, its stability enhanced by presence of Fe in coating.