The use of coated steel in concrete

摘要

Corrosion of steel reinforcement is the main cause for reduced service life of concrete structures. One of the preventive measures is the application of protective coatings on steel bars: galvanic or organic. Organic coating is one or more layers of interconnected materials (usually epoxy components) on the surface and generally efficiently protects steel against corrosion. But in the case of mechanical defects, its efficiency is significantly reduced due to pronounced localized corrosion. Galvanic coating - a layer of zinc (zinc-iron alloys) metallurgically bonded to a steel surface - was proven to successfully delay corrosion of steel in concrete, but under specific conditions problems related to intensive anodic reactions of the coating might occur. The combination of both coatings (duplex system coating) was already implemented in complex industrial systems and it could also be used to protect steel reinforcement in concrete. Laboratory results of electrochemical measurements on duplex system coating in simulated concrete pore solution with Cl~- were compared to results on separate (galvanic and organic) types of coatings. Corrosion damage was assessed by SEM and Raman spectroscopy. Carbon steel reinforcement bars will be protected with all three system coatings and embedded in concrete, subjected to long-term wetting (with Cl~- solution) and drying cycles. All protective systems will be characterized by various electrochemical and physical corrosion monitoring techniques.