Cheadle's Corrosion Cure

The worst enemy of a ship at sea is not storm or submarine but salt water. It corrodes a ship's hull, propellers and condensers, greatly shortens a ship's life. Salt water has been brutal to the overworked ships of World War II; corrosion of their condensers (in which cold sea water is pumped through tubes to condense spent steam from the engines) has been so accelerated that many have to lay up every nine months for retubing. But a device to draw the sting from salt water has been developed by a Seattle marine engineer named Arley Cheadle.

Last week, with the approval of the Maritime Commission, Cheadle rushed his first big order to West Coast shipbuilders. First installations of his "marine electrolysis eliminator" will be in tankers' condensers.

The principle on which the device is based was discovered by a Cheadle partner named H. L. Durham, now retired. Puget Sound fishermen could not understand why their boats' propellers and metal rudderposts wore out so fast in the water. Durham thought it might be accounted for by electrolysis (the process by which an electric current in a liquid transfers metal from positive to negative poles).

Tests proved Durham right. He further found that the rotation of a ship's engines sets up a weak electric current, which charges a ship's metal. In salt sea water, which is an excellent electrolytic bath, the metal is swiftly eaten away. Durham had no idea where the metal went, but he hit on a simple way to stop it: suspending in the water another metal higher in the electrolytic scale. Thus, when he installed a piece of zinc, electrically wired to the ship, near a bronze propeller, the propeller picked up zinc deposits instead of losing bronze.

Durham & Cheadle then developed a zinc alloy for the job (pure zinc soon gets coated with an oxide that interferes with electrolysis), and adapted their discovery to protect condensers, hulls, bulkheads, ballast tanks, etc. The device has already worked well on dozens of ships. So far as condensers, specifically, are concerned, Cheadle figures that his electrolysis eliminator doubles or triples normal life.

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