Tribological challenges in ocean energy systems: Failure mechanisms, materials, lubrication strategies, and reliability roadmaps

The vast renewable energy potential of the oceans remains largely untapped, not due to a lack of energy conversion concepts, but because the moving components of wave, tidal, and current energy systems experience premature failure under the ocean’s aggressive tribological environment. This review dissects the coupled (multi-mode) phenomena of friction, wear, lubrication, corrosion, erosion, and biofouling that collectively dictate the reliability of marine energy converters. Moving beyond isolated failure analyses, it establishes a system-level framework that links component function, motion kinematics, and degradation pathways under real oceanic conditions. The synthesis reveals how mechanical stresses, and environmental agents coevolve to form self-reinforcing degradation loops, where corrosion debris, cavitation, and microbial colonization accelerate wear and frictional loss in ways conventional testing cannot replicate. By consolidating these insights, the study formulates the fundamental, unanswered questions that define the frontiers of ocean tribology such as how third-body dynamics, transient electrochemistry, and surface-adherent biofilms interact at the interface to control material durability. Addressing these gaps is pivotal to transforming tribology from an afterthought to a central design principle, enabling durable, predictable, and economically viable marine energy systems. • Tribological degradation governs durability across wave and tidal energy devices. • Offshore failure modes depend on component motion and environment. • Coupled wear, corrosion, and biofouling accelerate multi-mode degradation. • Single-mechanism testing fails to address offshore performance. • Predictive durability requires synergistic (rigs), component-level tribological testing.