Effect of mill scale on the long-term corrosion resistance of a low-alloy reinforcing steel in concrete subjected to chloride solution

This study investigated the corrosion performance of reinforcing steels in concrete exposed to flowing 3.5 wt% NaCl solution for 4 years. Two kinds of steels were selected: low-carbon (LC) steel and low-alloy (LA) steel with alloying element Cr. Both steels were prepared with two surface conditions: as-received one (with mill scale) and pickled one (removal of the mill scale). The microstructure of the steel-concrete interface was observed to investigate the effect of steel type and surface condition on the corrosion pattern. The results reveal that the corrosion resistance and the corrosion pattern of steels were largely influenced by the feature of the mill scale.