The resistance of stainless steel partly embedded in concrete to corrosion by seawater

Abstract

Synopsis The corrosion resistance of Type 316 stainless steel, partly embedded in concrete, partly exposed to stagnant seawater and partly exposed to flowing seawater, has been determined over various periods up to about 12; years duration. The exposure tests were carried out in full immersion and tidal conditions, on specially designed concrete blocks. Mild steel specimens were also tested for comparison. Corrosion of exposed stainless steel was localized, not extensive, and affected neither the strength nor ductility of the specimens. Contrary to expectation, crevice corrosion occurred on only one of the 42 test specimens, and only after 12½ years total immersion. It is considered that the alkalinity of the concrete was responsible for minimizing corrosion on both embedded and external areas of stainless steel. Ordinary Portland cement concrete gave more protection to the stainless steel than did sulphate-resisting Portland cement concrete due, it is thought, to the higher cement content of the former and consequent greater reserve of alkalinity. The higher proportion of tricalcium aluminate in the OPC concrete and its known effect in complexing chloride ions and delaying their ingress into concrete was also considered to be of great significance.