Optimization of Anticorrosive Zinc Coatings: Tuning the Adhesion of Zinc/Silica Contact by Interfacial Ternary Oxide Formation
Résumé
Formation of mixed compounds at interfaces between materials often has significant impact on the properties of the junction. With the goal of assessing if interfacial oxide mixing improves the adhesion of anti-corrosive zinc coatings on silica, we report an ab initio study of the structural, electronic, and adhesion characteristics of interfaces between zinc and zinc silicate. We show that, regardless the precise thermodynamic conditions, ZnO-rich zinc sili-cate interfaces are more stable than SiO 2-rich ones because their formation does not require breaking strong Si-O bonds. Moreover, we find that zinc adhesion at such ZnO-rich interfaces is by at least a factor two larger than that of the zinc/silica contact. Due to a dense network of interfacial Zn-O bonds, this improvement does not produce any unfavorable decohesion effects in the zinc deposit. The formation of an interfacial silicate layer enables the suppression of the weak zinc/silica interface, which is responsible for the poor zinc adhesion. The cohesive cleavage within zinc predicted for the complex zinc/silicate/silica junction offers a promising improvement of performances of anti-corrosive zinc coatings of Si-rich steel grades, of crucial importance in steel-making and automotive industries.
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