Modeling Corrosion Progression and Optimizing Predictive Maintenance Strategies for Marine Vessel Hulls: An Engineering Case Study of Coastal Operations in Nigeria

Abstract

Hull structural degradation due to marine corrosion remains a leading cause of unplanned dry-docking, cost overrun and safety risk for vessels operating in the aggressive tropical waters of West Africa. Conventional corrective maintenance often results in emergency steel renewal at excessive cost.  This study develops and validates a predictive maintenance framework for hull steel renewal based on corrosion rate modelling, non-destructive testing (NDT) mapping and lifecycle cost optimization for operation in Nigerian coastal waters. AH36 hull steel (15 mm nominal thickness) was modelled using a uniform corrosion rate of 550 μm/year derived from tropical immersion data, supplemented by pitting analysis with Pitting Factor 3.5. Ultrasonic thickness gauging on a 500 mm grid was simulated for a 4,400 m² wetted hull area. Corrective renewal at critical loss (4,350 μm, 71% remaining thickness) was compared with a two-stage predictive strategy (interventions at 5.0 and 7.5 years, 20% thickness-loss trigger). Critical thickness was intercepted at t = 7.91 years under corrective strategy, requiring 414.4 tonnes effective steel renewal (530 standard plates) at ₦1.512 billion and 45 days downtime. The predictive strategy reduced steel renewal by 35-40%, cost to ₦1.20 billion (20.6% saving) and downtime to 28 days. Predictive corrosion modelling integrated with NDT enables timely, cost-effective hull renewal and is recommended for fleet operators in tropical marine environments.