Microscopic mechanism of corrosion inhibition in cementitious materials by silane coatings in sulfuric acid: Experimental and theoretical insights

Silane-based materials are widely used to enhance the corrosion resistance of concrete by preventing the penetration of harmful substances. These materials can be categorized into permeable and film-forming types. In this study, isobutyltriethoxysilane (IBTS) and polydimethylsiloxane (PDMS) were chosen to represent each category. Their protective effects and microscopic mechanisms were investigated in cement exposed to sulfuric acid using experimental methods and molecular dynamics (MD) simulations. Results show that IBTS can penetrate the cement matrix and form a waterproof network, limiting the entry of water, which carries corrosive agents like SO₄²⁻, thereby reducing gypsum formation. On the other hand, PDMS can form a surface film that effectively blocks sulfuric acid attack. MD simulations revealed that IBTS binds strongly to the matrix through Ca-O bonds, while PDMS relies on hydrogen bonds to create a stable structure. Both silanes establish a positively charged barrier on the surface, effectively inhibiting the penetration of sulfate ions into the matrix. This barrier facilitates the detachment of sulfate ions from the surface, thereby mitigating sulfate-induced degradation. This study provides valuable insights for using silane materials to protect concrete from sulfuric acid corrosion and improve its durability.