After six years in continuous operation, early indication of depleted sacrificial anodes inside a three-phase separation vessel was revealed by the vessel’s anode monitoring system (AMS). The vessel, which was constructed of carbon steel, has been subjected to a highly corrosive environment due to the presence of acidic gases (CO2 and H2S) and high-salinity formation water typically encountered in upstream crude processing plants.
A qualitative corrosion assessment was conducted to evaluate the need to open the vessel one year ahead of the scheduled turnaround and inspection (T&I). The study included a review of the previous inspection history and the existing corrosion protection layers; namely, internal coating, sacrificial anodes cathodic protection, and corrosion inhibition. It was concluded that the vessel can be safely maintained in continuous operation for the proposed period with a recommendation to conduct frequent external inspections to screen for any localized corrosion. Inspecting the vessel one year later (i.e., after seven-year continuous operation) revealed that the sacrificial anodes depletion was between 80-90%, providing the necessary protection to the vessel. Consequently, this assessment led to avoiding unplanned lengthy shutdowns and unnecessary production loss.