Humphry Davy
Protection of ships' bottoms

From 1761 onwards, copper plating had been fitted to the undersides of Royal Navy ships to protect the wood from attack by shipworms. However, the copper bottoms were gradually corroded by exposure to the salt water. Between 1823 and 1825, Davy, assisted by Michael Faraday, attempted to protect the copper by electrochemical means. He attached to the copper sacrificial pieces of zinc or iron, which provided cathodic protection to the host metal. It was discovered, however, that protected copper became foul quickly, i.e. pieces of weed and/or marine creatures became attached to the hull, which had a detrimental effect on the handling of the ship.

The Navy Board approached Davy in 1823, asking for help with the corrosion. Davy conducted a number of tests in Portsmouth Dockyard, which led to the Navy Board adopting the use of Davy's "protectors". By 1824, it had become apparent that fouling of the copper bottoms was occurring on the majority of protected ships. By the end of 1825, the Admiralty ordered the Navy Board to cease fitting the protectors to sea-going ships, and to remove those that had already been fitted. Davy's scheme was seen as a public failure, despite success of the corrosion protection as such. As Frank A. J. L. James explains, " the poisonous salts from copper were no longer entering the water, there was nothing to kill the barnacles and the like in the vicinity of a ship. This meant that barnacles could now attach themselves to the bottom of a vessel, thus impeding severely its steerage, much to the anger of the captains who wrote to the Admiralty to complain about Davy's protectors."
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