Silane films on galvanized surfaces: A review on the sol-gel deposition methods, influential parameters and characterization methods

Galvanized steel needs surface preparation before application of paint coatings to enhance adhesion and corrosion resistance. Surface preparation usually includes physical and/or chemical cleaning and conversion coating process. Conversion coating provide higher corrosion resistance and better adhesion to the polymeric top coat leading to longer lifetime. Chromate based conversion coatings were widely used in industrial applications for their considerable corrosion resistance. However; it showed carcinogenic and toxic effect for human and environment, which led to the replacement of these coatings. One of the replacements is silane compounds which are considered as green compounds due to the restricted side effects on human and environment. It is shown that these compounds have considerable corrosion resistance and in particular cases higher than that of chromate compounds. This paper reviews the parameters affecting the deposition of the organosilanes on galvanized steel, dopants effects and the methods used for characterization and evaluation of the deposited film properties.