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WILMINGTON, DE, May 1, 2007

Anode Fights Boat Drive Corrosion With Crucial Aid of DuPont™ SuperStructural Nylon

Mercury Marine has developed an innovative, robust anode for combating corrosion of marine propulsion drives using a SuperStructural grade of DuPont™ Zytel® nylon. The anode is part of a system for protecting metal parts of marine drives against corrosion when boats are docked or moored. Its operating principle is the same as that used for corrosion protection of offshore drilling rigs, bridge platforms and other high-value constructions.

Mercury Marine’s new anode consists of a titanium plate coated with ceramic

Mercury Marine’s new anode consists of a titanium plate coated with ceramic that is protected in a rugged housing injection molded from DuPont™ Zytel® 75LG40HSL. Consisting of PA66 polymer reinforced with 40 percent by weight of long glass fibers, the resin is part of the DuPont™ SuperStructural Solutions portfolio.

“The DuPont material,” said Scott Olig, polymer engineer, Mercury Marine, “allowed us to develop an anode that can perform and endure fully immersed in a conductive and corrosive underwater environment. In addition to having inherent corrosion resistance, it meets needs for high load-carrying capacity, resistance to abrasion or impact damage by sand, grit or underwater objects, stable dielectric properties and ability to hold exacting dimensional tolerances.”

Mercury Marine’s ceramic-coated anode

The new anode delivers major advantages over alternative anti-corrosion systems for marine drives, according to Olig. One such alternative uses “sacrificial” anodes that preferentially corrode in conductive or corrosive water. They require periodic replacement, which often entails swimming beneath the boat and using tools while underwater. Another alternative uses impressed-current anodes made of platinum-coated titanium, which are easily damaged by sand, grit and underwater objects. To reduce damage risk, such anodes are mounted near the boat transom rather than near the drive they protect. This means that the electrical current they emit must pass over a longer distance through water, which increases output draw from the boat’s battery or an on-shore power source. Mercury Marine’s new ceramic-coated anode, by contrast, is protected by its rugged SuperStructural nylon housing and abrasion-resistant ceramic substrate.

Thanks to its robustness, the new anode can be mounted underwater on the hull, close to the boat’s propeller and drive train. The housing is hermetically sealed to the hull, and the anode is connected electrically by wire to a power source within the boat and to a reference electrode placed at a calculated distance away.

“DuPont provided valuable assistance in our development of the anode housing,” said Olig. “This included the recommendation of the long-glass-reinforced Zytel® nylon grade we selected and mold flow analysis that were quite helpful in optimizing mold design and processing parameters.”

Mercury Marine injection molds the housing and assembles the anode at its molding facility in St. Cloud, Florida. The tooling was also produced by Mercury Marine.

The new anode system made its commercial debut in April as part of the Zeus™ drive for large diesel-powered craft from Cummins-MerCruiser Diesel, a joint venture partnership of Cummins Inc. and Mercury Marine, a division of Brunswick Corporation. In the future, the anode could be used to protect inboard or outboard marine drives of any size or power rating.

For more information about the Zeus™ drive, visit For more information about Mercury Marine products, visit or your nearest dealer.

DuPont™ SuperStructural Solutions includes a family of engineering polymers reinforced with glass, aramid or carbon fibers to provide strength and stiffness that helps bridge the performance gap between traditional engineering plastics and metals.

DuPont is a science-based products and services company. Founded in 1802, DuPont puts science to work by creating sustainable solutions essential to a better, safer, healthier life for people everywhere. Operating in more than 70 countries, DuPont offers a wide range of innovative products and services for markets including agriculture and food; building and construction; communications; and transportation.

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May 2007

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Photo: DuPont
Anode (circled in photo) is mounted in a water intake plate on the Zeus™ marine drive itself rather than in a remote boat location, thus reducing current draw needed for effective corrosion protection.

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