Monomeric Additives on Chemical Resistance of SPC Compositions

Influence of Monomeric Additives on Chemical Resistance of SPC Compositions 

Corrosion stability of SPC in high-concentration acid media permits its use widely in anticorrosive techniques. However, the corrosion resistance of SPC in alkalis and in weak water solutions of acids is not enough. The effect of corrosion in such environments is shown in deposits of salts in pores, cracks, and other voids. Crystallization of these salt deposits, introduced by the corrosion environment or formed by chemical reaction of the material and environment, leads to destruction of a silicate composition. 

Highly diffusive penetration of SPC can be drastically lowered by active additives that are capable of raising SPC density, and, therefore, its corrosion resistance. As indicated previously, the most effective results were obtained by introduction of FA or TFS additives. Addition of monomeric additives to silicate composition improves the physical-mechanical characteristics and chemical resistance of silicate compositions due to improvement in the quality of silicate bonds and better adhesion between the binder and coarse filler [1], In other words, the influence of the monomeric additives is conditioned by consolidation of liquid glass gel during hardening and modifications of alkaline components due to inoculation of furan radicals. 

The consolidation mechanism of SPC compositions containing these additives can be considered as resulting from two processes decompression of silicon acid gel due to a decrease in the surface tension of intermicellar liquid and polymerization under the influence of acid solutions. 

Considering FA and TFS as consolidation additives, it should be noted that penetration of the SPC compositions modified by FA strongly depends on concentration of an aggressive environment. The polymerization rate of FA in the silicate media under the action of aggressive environments depends on pH, especially in the first reaction stages. Corrosion of silica by hydrofluoric acid occurs rather quickly and leads to loosening of the SPC composition and an increase of diffusive penetration. Consequently, application of the consolidation additive FA is desirable at pH 5. 

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