Measuring Anode and Cathode Degradation


The anodes were cleaned, weighed, and installed on 2-foot lengths of 3/4-inch, copper pipe (type M), which were also weighed. We hung the samples between slips in the mid-Chesapeake Bay near Rockhold Creek for one year, cleaning quarterly to mimic light use. At the end of the test period, the samples were cleaned with a plastic scraper and scrub brush, and their interiors were scrubbed with a snugly fitted multi-knotted rope. Testers gave them a light acid cleaning to loosen barnacle residue and scrubbed them again before weighing them. We also measured potential driving force and current for each anode before and after exposure. Salinity at the test site varied from brackish to seawater salty. We will be testing in full-strength salt water for a followup article.


1. For testing, we mounted a variety of anodes to plain-copper tubing. This photo shows the samples before they were suspended in brackish water for a year. From left to right, they are the Sea Shield aluminum Streamlined with nail polish, Sea Shield zinc Streamlined with nail polish, Sea Shield aluminum Streamlined with grease, zinc Camp X-2, aluminum CMP Martyr, zinc CMP Martyr, Sea Shield aluminum Streamlined, Sea Shield zinc Streamlined, and the control (no anode).

2. After a year in the water, the anodes had a fair bit of marine growth. This photo (samples in the same order as photo #1) shows the test field after slight cleaning. Note that the aluminum anodes have barnacles, but the more-toxic zinc anodes and the unprotected copper tube do not.

3. Testers weighed each anode sample before and after the year-long test to gauge degradation level. The weights and percent of weight loss are shown in the accompanying Value Guide.

Darrell Nicholson, editor of Practical Sailor, grew up boating on Miami’s Biscayne Bay on everything from prams to Morgan ketches. Two years out of Emory University, after a brief stint as a sportswriter, he set out from Miami aboard a 60-year-old wooden William Atkin ketch named Tosca. For 10 years, he and writer-photographer Theresa Gibbons explored the Caribbean, crossed the Pacific, and cruised Southeast Asia aboard Tosca, working along the way as journalists and documenting their adventures for various travel and sailing publications, including Cruising World, Sail, Sailing, Cruising Helmsman, and Sailing World. Upon his return to land life, Darrell became the associate editor, then senior editor at Cruising World magazine, where he worked for five years. Before taking on the editor’s position at Practical Sailor, Darrell was the editor of Offshore magazine, a boating-lifestyle magazine serving the New England area. Darrell has won multiple awards from Boating Writer’s International, including the Monk Farnham award for editorial excellence. He holds a U.S. Coast Guard 100-ton Master license and has worked as a harbor pilot and skippered a variety of commercial charter boats.


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