What method did Sir Humphry Davy test to protect copper-covered ships from saltwater corrosion?

To protect the copper sheathing of ships from saltwater corrosion, Sir Humphry Davy utilized electrochemical methods involving the attachment of iron and zinc plates to the copper.1

By applying these plates, he intended to prevent the electrolytic corrosion of the copper by causing it to act as the cathode of an electrochemical cell, a process now known as cathodic protection. Although Davy successfully demonstrated the underlying protective principles, the method ultimately failed in practice because it led to significant fouling of the ship's hull, a result that caused him considerable frustration.21