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.