Extreme-Environment Coatings for Offshore Renewable Energy Systems: Coupled Degradation, Testing, and Lifecycle Design

Offshore renewable energy (ORE) systems experience interacting chemical, biological, and mechanical stresses that make coating performance dependent on component duty and maintenance access. This critical narrative review evaluates conventional and advanced coatings across atmospheric, splash, tidal, and submerged zones, distinguishing laboratory demonstrations from field evidence. Coupled degradation is analyzed in relation to coating architecture: strain-assisted ingress and delamination in organic multilayers; cathodic disbondment in immersed barrier systems; sacrificial consumption in metallic and duplex systems; and wear-induced loss of support in ceramic-rich layers. Surface preparation, layer dimensions, filler dispersion, and wet interfacial properties govern these pathways. Component-specific multi-stressor protocols use matched controls to distinguish interaction from coincident damage. An explicitly illustrative worked example links assumed defect-area histories to a remaining protective life of 2.64 years, repair area, discounted intervention cost, and climate impact. Growth-rate and access-delay scenarios show why these outputs require site calibration and cannot be treated as validated offshore predictions. Qualified multilayer organic and metallic–organic systems remain practical reference options, while nanofillers, self-healing, and sensing functions require demonstrated benefits at matched thickness, cure, and damage state.