Effect of Na3PO4 addition in mortar on steel reinforcement corrosion behavior in 3% NaCl solution

• The Na3PO4 addition in mortar decreases the chloride effect on localized corrosion.
• FePO4 and Fe3(PO)2 formations on anodic sites of steel protects against corrosion.
• The acoustic emission technique is a powerful tool to monitor the corrosion process.

The influence of a phosphate inhibitor on the corrosion behavior of steel reinforcement in mortar immersed in 3% NaCl solution was investigated. For this purpose, characterization methods (SEM, XRD), mechanical (flexural strength and compressive strength), electrochemical and acoustic emission measurements were carried out. It was demonstrated that the addition of phosphate inhibitor induces a slight decrease of the mortar compressive strength but no change of the flexural strength. The electrochemical measurements indicate that the addition of Na3PO4 in mortar leads to an improvement of the steel reinforcement corrosion resistance in chloride solution. It was also confirmed by the acoustic emission technique that the phosphate inhibitor decreases the corrosion rate. Furthermore the visual observation of the mortar corroborates these results. Thus it can be concluded that the addition of this phosphate inhibitor in concrete decreases the chloride ions effect on localized corrosion.