The heat-treatable and weldable alpha-beta titanium alloy, UNS R55400was developed as a higher strength alternative to the highly corrosion-resistant UNS R56404 (ASTM Grade 29)titanium alloy used as tubular components for corrosive, extreme high pressure, high temperature (XHPHT) and deep water hydrocarbon production service. Recently approved for sour service,1 this alloy exhibits very comparable resistance to UNS R56404 in acidic, sour and non-sour chloride-rich aqueous environments commonly associated with upstream and offshore hydrocarbon production. This paper presents an expanded laboratory test database on critical corrosion modes for UNS R55400 pipe exposed to relevant oilfield production environments which include sour well fluid brines, a heavy chloride/bromide brine well completion fluid, injected methanol, organic acid- and HCl-based well acidizing solutions, and seawater. The alloy’s elevated reducing acid chloride resistance exhibited in these tests is correlated with electrochemical parameters derived from cathodic/anodic polarization testing and alloy corrosion rates derived from dilute boiling HCl media. Corrosion performance comparison between UNS R55400 and other common high strength oilfield titanium alloys is made across these specific production service environments to provide guidance for alloy selection and use.
Key words: downloadable, titanium alloy, oilfield, stress corrosion cracking, sour brine, crevice corrosion, chlorides, methanol, seawater