Hydrogen embrittlement might be an issue for titanium alloys due to risks of brittle hydrides formation or interactions with external hydrogen. In industrial applications, much of the hydrogen absorption occurred in high conductivity sea or brackish water conditions. Hydrogen entry into titanium alloys of grades 2 (commercially pure titanium) and 5 (TA6V) was studied under natural seawater conditions. Exposures under cathodic protection conditions using zinc anodes and under over-protection conditions at -1300 mV/SCE at 20 and 80°C were performed up to 1 year. Hydrogen content was characterized by thermal desorption analysis and hydrides were observed on cross sections. Influence of the microstructure on hydrogen absorption and hydrides formation was determined.