Hybrid nano/micro-particles for Increased Steel Corrosion Resistance: Particles’ Alterations with pH Change and Steel Behavior in Cement Extract and Mortar

ABSTRACTHybrid nano/micro particles were investigated for their possibility to re-structure within local pH alterations, release certain active substance and further contribute to increased steel corrosion resistance. Two aspects with regard to corrosion control and self-healing in cement-based materials are discussed: the first aspect deals with the electrochemical performance of low carbon steel electrodes (St37) in model alkaline solutions (cement extract) in the presence of 4.9.10-4 g/l hybrid particles i.e. cement extract, containing PDADMAC (poly (diallyl, dimethyl ammonium chloride) / PAA (Poly (acrylic acid)/ PDADMAC over a CaO core. The second aspect refers to the performance of reinforcing steel (FeB500 HKN) in mortar specimens, containing hybrid particles in the mixing water in concentration of 3.6×10-4 wt. % per mortar weight. The main objective was to determine if these hybrids will lead to increased corrosion resistance of the steel surface layers, generally formed in the hereby investigated environmental medium (both liquid i.e. cement extract and solid i.e. mortar). Further, it was expected that when chlorides are involved, as corrosion accelerating factor, the presence of hybrid particles will delay corrosion initiation and will therefore lead to increased corrosion resistance. The results denote for indeed superior corrosion performance of steel in chloride-free and chloride containing medium, when hybrid particles are involved. The responsible mechanisms are related to increased barrier effects of the formed layer and self-repair upon morphological alterations of the hybrid particles, “nucleation sites effects” and/or Ca-core “release” on locally active (anodic) areas on the steel surface.