Atmospheric corrosion of steel reinforcing bars produced by various manufacturing processes

The aim of the present investigation is to evaluate the effect of manufacturing process upon the performance of reinforcing steel bars against atmospheric corrosion. Reinforcing steel bars produced by different manufacturing methods were exposed to the atmosphere in Athens for different periods of time. The progress of corrosion was evaluated by measuring the thickness of the corrosion layer formed on the surface of the bars. The morphology of the corroded layer was studied by optical and scanning electron microscopy (SEM), while X-ray diffraction analysis was used to identify the mineralogical composition of the corrosion products. Independently of the manufacturing process used, the main corrosion product formed was lepidocrocite (γ-FeOOH), followed closely by akaganeite (β-FeOOH) and goethite (α-FeOOH). Furthermore, it was found that the surface condition and the initial oxide layer on the steel bars, which is closely related to the manufacturing process, played a major role in the development of corrosion in atmosphere. Work-hardened reinforcing steel bars were found very sensitive to exhibition in the usual atmospheric conditions, followed by the Tempcore steel bars. The hot-rolled bars, either unalloyed or microalloyed with vanadium, presented the best corrosion behavior.