Corrosion assessments based on available data or modelling are necessary for end-user material selection, yet there is limited data to specific well conditions. For subsea landing strings, various alloys are used, and due to the chemistry and corrosivity variation from one field to another, a study was conducted to investigate the corrosion performance of four specific alloys for the application.
Experiments were performed in a high-pressure, high-temperature (HPHT) autoclave and corrosion rate was measured using weight loss (WL) method and rotating cage autoclave with WL coupons. After each experiment and WL measurements, the coupons were studied for pitting corrosion using profilometry
scans.

Four alloys, UNS(1l K21590 (F22), UNS G41400 (4140), UNS G86300 (8630) and UNS S17400 (17-4PH), were evaluated in HPHT autoclaves for corrosion under three different environment conditions varying in temperature (60°C and 150°C), H2S and CO2 partial pressures, and shear stress in HPHT
autoclaves. The comparison showed that the corrosion rate for all the studied alloys increased as partial pressures of the acid gases increased and temperature decreased. Between the three low alloy steels studied in this work, UNS G41400 performed worst, especially at a lower temperature. As expected, alloy UNS S17400 showed the best performance and the lowest corrosion rates. Profilometry studies showed no evidence of localized corrosion and pitting in all four alloys.