Reaction between sodium monofluorophosphate and portlandite and impact on steel reinforcement corrosion inhibition

The chemical products generated in the reaction between sodium monofluorophosphate and cement paste, simulated by a calcium hydroxide solution, were analysed using X-ray diffraction and transmission electron microscopy with energy dispersive X-ray analysis. Portlandite, apatite, fluorite, calcite and amorphous products were identified as the main synthesized phases. Nanoparticles of hydroxyfluoroapatite (Ca-5(PO4)(3)(OH,F)) were also profiled. In a medium of high alkalinity such as the tested experimental conditions, PO3F2- is decomposed into PO43- and F- ions, placing its utility as a corrosion inhibitor for steel reinforcements in doubt. (C) 2012 Elsevier Ltd. All rights reserved.