Novel anticorrosive zinc phosphate coating for corrosion prevention of reinforced concrete

Abstract

Deterioration of reinforcing concrete structures is a common problem among all the coast countries. Every year, several billion dollars are spent to repair and maintain reinforced concrete structures. Over time, the metal reinforcing bars used to improve the properties of concrete become susceptible to corrosion due to factors such as the presence of chloride and carbonation. Present work includes the use of novel anticorrosive coating. The use of zinc phosphate (ZP) coating has advantage of the low solubility of phosphates in medium- or high-pH solutions; also the resulting coating remains adhered to the metal surface even under extreme deformation. This study presents the efficiency of a new inhibitive pigment ZP containing zirconium compound obtained by chemical conversion (CC) method and cathodic protection to protect the steel rebars against localised corrosion in concrete. The corrosion behaviour of coated steel was assessed by open circuit potential, potentiodynamic polarisation and electrochemical impedance spectroscopy. Firstly, results demonstrated that the new coating show an adsorption on steel surface and provides an effective corrosion resistance compared to carbon steel rebar. Secondly, results showed that the increased weight of coating made by CC is consistent with the development of the polarisation resistance and corrosion potential of samples studied. Thirdly, a reduction in the corrosion rate is obtained once the coating covers the surface of the metal.

Keywords:

• concrete
• corrosion
• chloride
• carbon steel
• zinc phosphate

Disclosure statement

No potential conflict of interest was reported by the authors.