Advancing Ship Rudder and Appendage Protection: Glass Flake Epoxy Primers for Cavitation and Corrosion Resistance in Marine Applications

Rudder and appendage structures on seagoing vessels operate in one of the harshest marine environments, where hydrodynamic loading, cavitation, high-velocity seawater, and fluctuating electrochemical protection converge.Conventional antifouling and epoxy coating systems, while effective for biofouling control, are unable to maintain barrier performance during periods of impressed current cathodic protection (ICCP) shutdown.This study investigates a reinforced barrier approach using a 300 µm glass flake epoxy (GFE) primer beneath conventional antifouling. Data from 125 drydock inspections of LNG, LPG, Ultra-large crude carriers (ULCCs), and container vessels revealed recurrent spot pitting, coating delamination, microbial corrosion, and cavitation erosion particularly in ICCP-off intervals. Field deployment of the GFE system across 18 LNG vessels showed a 95% reduction in corrosion-related defects, an 87.5% reduction in pitting rate, and significantly extended repaint cycles. Mechanistically, GFE’s tortuous-path barrier, low water-vapor transmission rate (WVTR), and higher modulus impart dual protection against cavitation-induced coating breakdown and electrochemical attack during ICCP outages, improving appendage integrity and lifecycle economics.