Boat owners have always embraced innovation. They have an innate ability to see the benefit of a new product or technology, and how it will affect their time on the water. Except for anodes. In the face of modern alternatives, generations have continued to rely on zinc for salt water and magnesium for fresh. Performance Metals offers a brief overview of the science of galvanic corrosion and insights on how best to leverage advances in metallurgy to better protect a vessel, in all water salinities.
Galvanic corrosion occurs when dissimilar metals, say stainless steel and bronze, make contact in a moist or submerged environment. It creates a battery of sorts—even without electrical power on the boat. One of the two metals becomes ‘sacrificial’, and gets eaten away. This can be a propeller shaft, outdrive or inexpensive, easily replaced anode.
Two metals have traditionally been used for anodes: zinc and magnesium. Each has its merits, but with varying results depending on the environment and application.
Over time, zinc hydroxide forms an insulating barrier, reducing its effectiveness. This grey deposit can be scraped away, but is often difficult to access, especially when in the water. Zinc does not protect in fresh water and is questionable in brackish. It’s also environmentally toxic. The US EPA has identified it as a major source of pollution in marinas. It’s so harmful, the state of Maryland is considering banning it.
Magnesium is the least noble of anode metals, meaning it corrodes the quickest and offers no protection in salt and brackish water. It’s so effective, it can easily overprotect aluminum hulls, outboards and outdrives in polluted water—even a few hours immersion can result in paint being lifted off.
Modern alternatives are available, however. Lightweight Navalloy® is a proven aluminum alloy that protects in salt, brackish and fresh water. It lasts 30% longer than zinc and up to four times that of magnesium. Cadmium free, it is 20 times less toxic than zinc. A trace of indium prevents oxidation and the maintenance required for zinc. It meets military specification MIL-DTL-24779B(SH) and ABYC standards.
Made in the USA, Navalloy anodes feature the company’s patented Red Spot Wear Indicator. When it becomes visible, it’s time to replace it.
Performance Metals’ website hosts a wealth of technical information for OEMs, custom boatbuilders and boat owners on their website: www.performancemetals.com