Coatings for corrosion protection of steel used in reinforced concrete

Abstract Silicon and silicon-titanium protective coatings were deposited on steel rebars, wires and fibers using a novel chemical vapor deposition technique that combines the low cost of pack metallization with the advantages of subhalide chemistry and with the high heat and mass transfer of a fluidized bed reactor. The steel samples were immersed in a bed of silicon or silicon-titanium particles fluidized by an argon-0.1% HCl mixture and kept at temperatures ranging from 400 to 750°C. Diffusion coatings were obtained in all cases. Coating rates of over 1 μm min −1 were obtained at the highest temperatures. Selected coated samples were tested for corrosion resistance by chemical and electrochemical techniques. In general, silicon provided some corrosion protection as expected. A.c. impedance measurements in acidic chloride solutions indicated that very thin and very thick silicon coatings were as protective as coatings 1–5 μm thick. The best coatings were obtained when silicon and titanium were codeposited at temperatures around 550°C. These coatings increased the corrosion resistance by more than an order of magnitude with respect to the uncoated sample.