Modified Zinc Phosphate Coatings: A Promising Approach to Enhance the Anti-Corrosion Properties of Reinforcing Steel

Abstract

Zinc phosphate conversion coatings are widely used for increasing corrosion resistance and surface preparation for painting. This kind of treatment has recently been introduced in the field of reinforced concrete. However, the disadvantage in the use of such coatings is the existence of pores. Zinc phosphating baths have constantly been developed and modified by additives in order to enhance the coating characteristics including the corrosion resistance and the alkaline stability. These additives and their effects on the resulting coating were reviewed in the current paper. The mechanism of phosphate coating formation, the alkali stability of the coating and the disposal of the phosphating sludge were also briefly reviewed.