Titanium alloys have been considered during the last several years as an alternative to steel and flexible (non-bonded) pipe for deepwater applications. Titanium alloys offer some distinct technical advantages for such applications, such as low elastic modulus, high strength-to-weight ratio, excellent general and localized corrosion resistance, and high fatigue resistance in air and in seawater. However, a major consideration in the suitability of titanium for extended subsea service is its potential susceptibility to hydrogen embrittlement in seawater under exposure to cathodic protection potentials intended for neighboring steel components. This paper examines Ihe susceptibility of several titanium alloy grades to hydrogen embrittlement, and highlights potential mitigation measures. Selected laboratory and field test data and a preliminary predictive model are presented in part of the discussion. It is concluded that proper alloy grade selection, and use of suitable mitigation measures are key to successful use of titanium alloys in extended subsea service.
Keywords: Titanium, offshore applications, subsca service, cathodic protection, hydrogen embrittlement, model, mitigation.