Tuesday, April 26, 2011

Sir Davy and the Royal Navy

Fortunately science, like that nature to which it belongs, is neither limited by time nor by space. It belongs to the world, and is of no country and no age. The more we know, the more we feel our ignorance; the more we feel how much remains unknown...
 ~Sir Humphry Davy, November 30, 1825

Sir Humphry Davy (1778-1829)
Sir Humphry DavyByronic scientist extraordinaire and mentor to Michael Faraday, scientist plus extraordinaireonce proposed a clever solution to a problem vexing the Royal Navy. But his idea led to unintended consequences. Davy was publicly embarrassed by the Admiralty, and his career never recovered and set the stage for Faraday's rise to the epitome of British science. Sadly, Davy's health also faltered (a possible consequence of chlorine and fluorine gas inhalation). Here's the fascinating story:
 ... at the beginning of 1823...the Navy Board (which provided the Royal Navy's civilian administration) approached Davy about the possibility of protecting the copper sheeting of warships from the corrosive effects of seawater. The naval budget had been reduced by 71.4% since the end of the war of 1815, and hence the Navy Board was seeking to lower expenditures. If the frequency with which ships needed to be dry docked to replace their corroded copper could be reduced, then significant savings would be made.
During 1823, the Navy Board provided Davy with information about copper corrosion and following his return from holiday at the end of October, he began investigating the problem. By mid-January 1824, he concluded that there existed an electrical reaction between the copper and the oxygenated seawater (no corrosion occurred when oxygen was not present) which allowed the formation of various copper salts. Thus he reasoned, that if the electrical polarity between the copper and the seawater was reversed, the corrosion would cease. In his Elements of Chemical Philosophy (1812), he had ranked the electro-chemical reactivities of various metals. Zinc was much more electro-positive than copper-which suggested that a relatively small amount attached to the copper would prevent the corrosion.*
...the Admiralty ordered that practical tests should be carried out on three warships moored in Portsmouth Dockyard. Starting in mid-February 1824. Davy's "protectors" as they were called were attached to their copper, the state of which was monitored in the ensuing months. Faraday, who undertook most of the follow-up experiments, visited Portsmouth once. At the end of April, satisfied that the tests were successful, the Navy Board drafted an order that the entire fleet be fitted with the protectors...and the fitting programme was undertaken during the remainder of the year and into 1825. However...problems began to appear, and by the summer it was clear that the Navy faced a major disaster. Ships returning from the West and East Indies were found to have their bottoms, though preserved, fouled with seaweeds, barnacles, and suchlike. Because of the protectors, no longer were the poisonous salts produced by the corroding copper being released into the water to kill the source of the fouling. Davy...had tried by varying the ratios of protectors to copper to prevent it, but such was the rush and inadequacy of the Portsmouth trials, that...the Admiralty ordered the removal of the protectors.
Then there followed the political task of allocating the blame for the disaster. The Navy Board had protected itself by doing only what the Admiralty ordered. Hence in the eyes of the Admiralty...Davy was to blame. This failure doubtless contributed to Davy's ill health and premature resignation as President of the Royal Society on 6 November 1827.
~Frank A.J.L. James Michael Faraday: A Very Short Introduction, Oxford University Press (2010)

Two years later, Davy was dead at the age of 51.


  1. *Sacrificial zinc anodes were later used (and still are used) to protect steel tanks, rails and ship hulls from rusting. Since zinc oxidizes more easily than iron, it corrodes first. When the anode is mostly consumed, it can simply be replaced.

  2. If only they'd considered anti-fouling paint, the copper, the sacrificial zinc and Davy's reputation would have all been vindicated.

  3. Odd you should mention paints, which weren't well developed then. I learned from the same book that Faraday oversaw the painting of lighthouses along the coast of Britain, introducing the use of lead carbonate (white) and lead oxide (red). These pigments are indestructable and gave us the iconic image of the lighthouse: link

  4. Wow, that photo got taken down fast! Try this one instead.