Corrosion resistance of CaO–Al2O3–SiO2 glasses used for flame spraying on concrete

Concrete components can severely suffer from corrosion during their service lifetime. To achieve higher durability, glass coatings can be applied onto the concrete surface for protection purposes. Current solutions for protection measures are either sticking thin glass panes onto the concrete or applying plastic layers using flame spraying. The aim of this work was to develop an optimised glass composition for protective layers, in order to be suitable for flame spraying on concrete. The main advantage of this process is the deposition of continuous and joint-free glass layers onto complex geometries. Dense glass layers provide a much higher corrosion resistance and lifetime compared to polymer layers. The challenge encountered by these glass coatings resides in the contact with strong acidic fluids on one side and with the alkaline concrete on the other. Therefore, a new glass appropriate for flame spraying has been developed. The composition of this glass is cheaper compared to established reference glass products while providing comparable alkaline resistance. As the acid resistance of this glass is not sufficient, in order to ensure the desired requirements of an adequate corrosion protection, a multilayer glass coating was developed, in which the first layer consists of the alkaline-resistant CaO–Al2O3–SiO2 glass and the second layer of an acid-resistant glass.