Assessment of Corrosion Prevention and Control Practices on Oil and Gas Pipelines Operated by NNPC in Edo State

Pipeline corrosion remains one of the most costly infrastructure integrity challenges facing Nigeria's state-operated petroleum transmission network, contributing to product losses, environmental contamination, and revenue leakage in the mid-stream sector. This study assesses corrosion prevention and control practices applied to oil and gas pipelines operated by the Nigerian National Petroleum Corporation across its Edo State network corridor. The research design combines document review of inspection and maintenance records, structured interviews with pipeline integrity engineers and cathodic protection technicians, and field assessment of selected pipeline sections using direct pipeline assessment methods. Corrosion monitoring data including external corrosion depth measurements, cathodic protection potential readings, and in-line inspection records were analysed to characterise the corrosion environment and gauge the effectiveness of existing mitigation measures. Findings indicated that 38 percent of monitored pipeline sections exhibited cathodic protection potential values outside the recommended range due to rectifier malfunctions and anode depletion. Internal corrosion rates were elevated in sections handling high water-cut production fluids, with wall loss rates exceeding API 570 threshold values in two locations. Coating assessment revealed holiday densities above acceptable limits on 29 percent of inspected segments. The study recommends an accelerated cathodic protection rehabilitation programme, deployment of chemical corrosion inhibitor injection at high-risk locations, and integration of real-time corrosion monitoring into the pipeline control system. Keywords: pipeline corrosion, cathodic protection, NNPC, corrosion monitoring, Edo State.