The combination of stress corrosion resistance, low density, low modulus and non-magnetic properties possessed by titanium alloys makes many of them suitable for service in sour conditions. Titanium has been successfully used in a variety of sour service applications in the drilling, logging and production phases of the oilfield industry. Sour service environments are defined by NACE International specification MR0175 as "fluids containing water and hydrogen sulphide (H2S) that is at a total pressure of 0.4MPa (65psia) or greater, and if the partial pressure of hydrogen sulphide in the gas is greater than 0.0003MPa (0.05psia)". The acidity of the environment is below pH 3.5, and carbon dioxide, and chlorides are also normally present. Titanium alloys are available in a range of strength levels, and this permits selection for a wide variety of oilfield and geothermal applications including pipework, manifolds, valves and pumps, chokes, kill and booster lines, instrument casi...