Controlled scratch testing has been applied to experimental coatings of the kind used on marine structures, based on epoxy-amine resins. Measurements of the scratch hardness and the critical load to failure have been made. Inspection of the scratch tracks by reflected light microscopy and scanning electron microscopy enabled identification of the failure mechanism. Failure could be by though-thickness cracking or adhesion failure. The failure mechanism is sensitive to the coating thickness and detachment from the substrate was obtained only from coatings less than 300 mum thick in the as-prepared state for tests conducted with a limiting load of 80 N. The deterioration of properties of samples immersed in hot seawater was very sensitive to composition.