Anticorrosive coating systems for marine propellers

Marine propellers work in a severe environment due to the highly corrosive seawater, biofouling, and high rotational speed. As a result, they can suffer from galvanic corrosion, cavitation, impingement, electrolysis, and microbial corrosion. Unprotected propellers attract undesirable marine growth to the propeller surface, adding extra weight and friction to the vessel to increase fuel consumption. In order to address these issues, various corrosion prevention strategies have been utilised. A thorough understanding of the critical coating properties for propeller coatings and their failure mechanism is necessary before designing an efficient anticorrosive coating system. This review provides a comprehensive and critical review of the current research status of the anticorrosive coatings that serve as candidates to be used on marine propellers. While Cr6+ containing coatings have been the most effective coating in preventing metal corrosion due to their ‘self-healing’ ability, Cr6+ has been recognised as carcinogenic and causes environmental pollution. The imminent ban of Cr6+ containing coatings in most countries means an urgent need to develop alternative eco-friendly anticorrosive coating systems to replace Cr6+ containing coatings. The viability of organic, inorganic, polymer, nanocomposite, molybdate and cerium-based corrosion inhibitors, conducting polymer, self-healing coatings, and integrated anticorrosive and antifouling coatings (IAACs) are being studied. It is believed that the future of propeller coatings design should be focused on coatings with multifunctional characteristics to inhibit the coating damage resulting from cavitation and electrolysis corrosion.