Effect of temperature on the marine immersion corrosion of carbon steels

Theoretical and laboratory studies indicate that the corrosion of mild and low-alloy steels should be a function of temperature. In practice, however, it is usually held that this cannot be discerned from actual field corrosion data, being confounded by many other influences. The present study considers data from a recent ASTM-sponsored field study, which reported observations for more than 5 years for the immersion corrosion at 14 different sites around the world for copper-bearing carbon steel (UNS KO1501). It also considers data reported historically in the literature, both for copper-bearing steel and for structural-grade steel. For these steels, general or uniform corrosion is the main interest because pitting is usually limited. When data is restricted to conditions that might be expected to prevail at sea and is carefully scrutinized and supplemented by information about (the likely) environmental conditions, it can be arranged to suggest that there is a clearly defined effect of temperature on corrosion behavior. This effect is consistent with laboratory observations but extends them in the lower temperature region even though the available data in this region is sparse, The dependence on temperature for steel is not inconsistent with earlier reported observations on the temperature dependence of 90:10 copper-nickel and aluminum. The effects of the degree of dissolved oxygen saturation and dilution by fresh water (and calcium carbonates) are apparent in the reported data, as is the influence of water velocity.