A comprehensive review of the corrosion and degradation behaviour of additively manufactured metals and polymers

Additive manufacturing (AM) has revolutionized the fabrication of complex metal and polymer components; however, corrosion and degradation remains a key limitation to their long-term reliability. Defects such as porosity, surface roughness, residual stress, and microstructural anisotropy often impair passive film formation and accelerate localised corrosion. Although AM is increasingly adopted in aerospace, biomedical, and marine applications, systematic studies on corrosion under real-world service conditions are still scarce. Moreover, the limited scope of existing AM-specific corrosion standards, particularly for polymers, complex lattices and coupled environmental exposures, hinders comparison among reported results. This review critically analyses the corrosion behaviour of AM metals and the environmental degradation behaviour of AM polymers fabricated via fused deposition modelling (FDM), stereolithography (SLA), selective laser sintering (SLS), selective laser melting (SLM), and electron beam melting (EBM), emphasising how process-induced defects and environmental factors (temperature, mechanical load, and humidity) influence degradation. Mechanistic insights into corrosion initiation, propagation, and defect–microstructure interactions are discussed alongside effective mitigation strategies, including coatings, surface treatments, and post-processing techniques. The review also identifies current gaps in standardisation and proposes recommendations for developing cost-efficient, AI-assisted design and testing approaches to enhance corrosion resistance and service life of AM parts deployed in aggressive environments.