Barnacle proteins protect metals from corrosion in salt water

Metal surfaces of boats and offshore rigs are coated with corrosion-inhibiting compounds to protect them in the high-salt environment of the sea. Commercial inhibitors are organic compounds based on azoles, amines, and phenols. They form tough films on metal surfaces, preventing exposure to seawater, but they can leach toxic chemicals into the environment, harming living organisms.

Because barnacles cling to underwater metal surfaces, researchers at Nanyang Technological University investigated whether the crustaceans’ adhesive proteins could form an impenetrable protective layer on metal.

The team genetically engineered bacteria to produce a recombinant protein of the barnacle Megabalanus rosa. Other researchers have made glues for bone or dental repair from this protein because it adheres strongly to inorganic substrates, says materials scientist and engineer Ali Miserez, who led the work.

The researchers immersed steel pieces in a concentrated salt solution that simulated seawater, and they added protein solutions of different concentrations. At concentrations over 5 mg/mL, the protein quickly adsorbed onto the steel surface to form a uniform layer. Spectroscopy analysis and computer simulations suggested that the protein formed a complex with free iron ions in the steel. “This complex effectively covers the metal substrate, preventing corrosion,” Miserez says.

“This is high-risk, high-reward work,” says Nick Aldred, who studies bioinspired coatings at the University of Essex. “It may not work, but if it does, the impact will be large.” A big challenge with biomaterials is that “protein layers tend to become food for bacteria very quickly,” he says, so it will be important to engineer proteins that do not quickly degrade in the environment.