Wed, 13 January, 2021
TWI’s Maria Eleni Mitzithra, a senior project leader in the Surface, Corrosion and Interface (SCI) Section, is due to present at the Marine Corrosion Forum on 21 January 2021.
The event, which is free to attend, will see Maria present on the ‘Exposure of Various Polymer Lined Carbon Steel Pipe Sections to a Sour Hydrocarbon Fluid at a Maximum Service Temperature: Methodology and Observations.’ The one-hour presentation will begin at 12PM GMT.
The work involved TWI’s expert on non-metallics, Technology Fellow Dr. Bernadette Craster, corrosion engineer, Dr. Maria Eleni Mitzithra and Team Leader-Sour Lab, Barnaby King. The work consisted of a Joint Industry Project, funded by Saudi Aramco, Subsea 7 and with contributions from the Core Research fund supported by the Industrial Members of TWI Ltd.
The acceptance of polymer-lined carbon steel pipe for sour hydrocarbon service under different conditions of temperature and pressure, is of increasing importance in field locations where corrosion is a concern. As part of this study, individual sections of polymer-lined steel pipe were exposed to a sour hydrocarbon mixture containing carbon dioxide (CO2), methane (CH4), hydrogen sulphide (H2S), deionised water and hydrocarbon fractions. The thermoplastic liners considered in this study were manufactured from four different resin materials; two polyamide grades (a PA type 1 and a PA type 2), a polyethylene with raised temperature (PE-RT) resistance and a polyvinylidene fluoride (PVDF). Non-metallic liners were installed in a 913mm length of seamless SCH40 API 5L (X52) steel pipe. Two liner venting systems were added at the same clock position but displaced axially. The fluid mixture, pressurised to 89barg, was displaced at 5ms-1 across the surface of the lined and unlined sections of pipe for a period of 180 days. The PVDF test pipe was exposed to the static fluid due to the high temperature of the testing. Lined pipes were tested at 80°C, 90°C and at 130°C depending upon the liner material specification. The test duration was 180 days with rapid decompression being performed at 90 and 180 day intervals in order to check for liner collapse resistance. Analysis was carried out on the unexposed and exposed liners. Unexposed X52 was analysed along with sections of the exposed lined and unlined X52 surface, including areas near the liner mechanical end termination and adjacent to the liner venting system. In general, all polymer liners acted as an effective barrier to corrosion of the pipe steel material for the specific test duration. Scales up to 16μm thick under the polymer liner were noted and the main detected phases were pyrrhotite, and pyrite. No sulphide stress cracking was detected on the metallic host pipe behind the liner. (NACE CORROSION 2020 digital proceedings, paper no. 14821).
The Marine Corrosion Forum allows for discussion and the exchange of information on materials engineering and wet corrosion matters. Established in 1988 as the ‘Marine Corrosion Club,’ the forum changed its name in 2003 and has interests in areas including coating technology, composites, corrosion engineering and design, desalination, chloride effects, erosion-corrosion, microbial induced corrosion, shipping and naval issues, corrosion protection, corrosion prevention and cathodic protection.