Aluminosilicate coatings with enhanced heat- and corrosion resistance

Abstract This paper summarizes the results of development of heat- and acid resistant mineral coatings intended for protection of concrete structures and brickwork from exposure of acid media and elevated temperatures. The protective coatings are produced basing on the alkaline aluminosilicate bonds, in which the alkaline compounds are strongly bound into water insoluble hydroaluminosilicate complexes. On the contrary to the known-in-the-art mineral coatings based on cements containing slag and slag/ash, the coatings based on the alkaline aluminosilicates advantageously explore a correlation between corrosion resistance and phase composition due to the synthesis in the structure of the alkaline aluminosilicate matrix of high-silica zeolite-like phases (faujasite, chabazite and mordenite). The introduction into the alkaline aluminosilicate matrix of the formula Na 2 O·Al 2 O 3 ·6SiO 2 ·14.5H 2 O of the acid resistant fillers, selected from mica, aluminosilicate microspheres and ground quartz sand taken in quantities of 3, 8 and 12 wt.% enabled to increase the acid resistance of the coatings by 1.25–1.5 fold compared to the known-in-the-art mineral analogs. Heat resistance of the coatings under study, in the conditions of alternate exposure of temperature (473 K) and vapors of oleum, may reach 100 cycles. The developed formulations of the anti-corrosion alkaline aluminosilicate coatings were successfully tried in 2007 in industrial conditions in repairing the deteriorated brickwork of the flue. After 5 years no sign of deterioration of the protective coating was reported.