The offshore energy production sector and many other industries rely on structures that are ageing and will continue to do so for the unforeseen future. This is particularly the case for many offshore oil and gas installations which are now clearly experiencing ageing and are in a life extension stage. Materials used in offshore structures are susceptible to degradation and deterioration processes as they operate in a hostile seawater environment, which over time can severely affect their properties. The key question asked is how long can materials and the structure where they are used perform their function safely without expensive intervention? The continued use and re-use of existing structures is of considerable importance and will be beneficial both for the economy and the environment.