Steel in concrete: Part II Electron microscopy analysis Available to Purchase

The microstructure, crystallinity and the chemical and mineralogical constitutions of corrosion products formed under exposure of a steel-reinforced concrete fence post to normal atmospheric conditions have been investigated by analytical electron microscopy techniques. A bi-layered structure is observed comprised of a dense inner spinel phase (Fe₃O₄,/γ-Fe₂O₃,) in epitaxial orientation to the steel substrate and a relatively porous outer layer of mainly χ-FeOOH. A weak but apparent band showing a relatively elevated chloride concentration, rims the inner corrosion layer. The permeation through the corrosion layer of the products of cement hydration is indicated by the detection of nodules of Ca(OH)₂, crystals at the steel reaction boundary. The mechanism of reinforced steel corrosion is thus evaluated on the basis 0fthese.finding.s and with special reference to the role of chloro-complexes and the modes of E_h, and p_H buffering actions in the composite steel-corrosion product-cement system.