Corrosion behaviour of metal inserts in simulated ancient masonry mortars

• Corrosion of metal inserts in aerial and hydraulic mortars was studied.
• Carbon steel, stainless steel and titanium inserts were considered.
• Mortar composition had a secondary effect on the corrosion rate compared to the role of moisture.
• High corrosion rate was measured only for carbon steel in mortars exposed to 95% RH or water suction.
• Mortar resistivity was found to be a reliable parameter to assess corrosion of embedded inserts.

Corrosion of metal inserts may be detrimental to the durability of masonry. The paper discusses corrosion of carbon steel, stainless steel and titanium embedded in aerial and hydraulic mortars simulating those of ancient walls. The effects of temperature (5–40 °C), moisture (65–95% RH and water suction) and electrical resistivity of mortars on the corrosion of metal inserts are discussed. Results showed that the corrosion rate of embedded steel, regardless of the mortar composition, is negligible in mortars exposed to 65–80% RH (even at 40 °C) and modest even at 95% RH, while high values were obtained in the presence of water uptake.