High temperature hard freshwater corrosion loss of mild steel

Some maritime structures may be exposed to higher temperature freshwaters and these can cause significant corrosion. Data obtained in a realistic experiment in which mild steel coupons were exposed for up to two years to hard freshwater at temperatures in the range 50-60°C are described and interpreted relative to the corrosion loss model earlier shown to be applicable to both seawater and fresh water corrosion. The model is reviewed briefly. It considers cathodic oxygen depolarization in the early stages of corrosion and the development of anoxic conditions that could permit the involvement of bacteria in the corrosion process. It is shown also that corrosion loss data for the hard tap water from Teddington, UK at 70ºC is consistent with the corrosion loss model. The trends derived from these data permit improved estimates to be made of the effect of water temperature on the longer-term corrosion loss of mild steels in both hard fresh waters and seawaters.