Abstract
The petrochemical plants in Arabian Gulf use seawater to remove exothermic heat generated in the reactors. In each plant, seawater is stored in large reinforced concrete reservoirs that provide cooling system to the plant. Most of these plants came on-stream in early 1980s. After only few years service, many of those seawater structures started showing signs of distress in the form of cracking and spalling of concrete resulting due to chloride-induced corrosion of the steel reinforcement. Cathodic protection (CP) systems were designed and installed to arrest corrosion of the reinforcing steel in the seawater structures.
The cathodic protection systems have an operating history of 8-10 years. Long-term performance and assessment of these systems are described and discussed. The monitoring data collected from these systems have shown that 100 mV decay criterion was met at most of the protected areas and as a result of CP application, free corrosion potentials of the steel reinforcement had been shifted towards less negative potentials by some 150 to 200 mV, exhibiting restoration of steel passivity in many areas. The results show that all CP systems are performing satisfactorily and meeting the design objectives in controlling the corrosion of the steel reinforcement. Visual condition of the protected areas of the structures are exhibiting no signs of deterioration of concrete or rust staining since the commissioning and operation of these CP systems. However, severe deterioration of concrete was noticed in some unprotected or under-protected areas of one structure.
