- Title
- Longer-Term Corrosion of Mild Steel in Near Stagnant Seawater
- Creator
- Chaves, I. A.; Petersen, R. B.; Melchers, R. E.
- Relation
- Australasian Corrosion Association Conference 2023. Proceedings of the Australasian Corrosion Association Conference 2023 (Perth, WA 12-15 November, 2023) p. 1-9
- Publisher
- Australasian Corrosion Association Inc.
- Resource Type
- conference paper
- Date
- 2023
- Description
- Both short and long-term marine corrosion performance of steels have been measured extensively for open sea exposed surfaces. However, for enclosed, near-stagnant, sea water conditions information is only anecdotal. This paper reports empirical data from an ongoing multi-year study in near stagnant seawater immersion corrosion conditions for 3 to 5m long mild carbon steel strips. The data are particularly relevant to the offshore renewable energy industry which often is unable to ascertain the extent of corrosion within windmill support piles. The results show that, although the strips are subject to atmospheric immersion tidal and splash zone corrosion, no evidence was found of the classical corrosion profile for vertical steel structures (e.g. piles) or of accelerated low water corrosion. In the vertical direction, regardless of exposure site, the pattern of general corrosion through the various zones remained similar throughout the different exposure periods. For each exposure zone the magnitude of that corrosion displays bi-modal behaviour as a function of exposure time, consistent with much other data. As expected, the exposure site with elevated concentration of dissolved inorganic nitrogen showed greater corrosion losses. It is proposed that the observed corrosion behaviour primarily is the result of the shielded quiescent environment. A reliability case study analysis was performed to highlight how the data obtained so far can be translated into risk estimates for practical decision making. Internal corrosion, although negligible by itself in terms of generating risk of failure, when taken in combination with external corrosion losses highlight that internal corrosion should not be dismissed, at least not for when 50 year design life is targeted.
- Subject
- mild steel; seawater; stagnant; offshore
- Identifier
- http://hdl.handle.net/1959.13/1500138
- Identifier
- uon:54857
- Language
- eng
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