How to Extend Zinc-Anode Life

Zinc anodes protect shafts, props, and other underwater metal parts on boats. Use this trick with nail polish to extend the lifespan of your zinc and reduce waste. Shoreline: Green Wakes from our December 2012 issue.

Extend Zinc-Anode Life
Paint a 1-centimeter stripe of nail polish on the zinc to extend its lifespan and reduce waste.Michael Robertson

Zinc anodes protect shafts, props, and other underwater metal parts on boats. Because zinc is less noble than stainless steel or bronze, it suffers the effects of galvanic corrosion more readily, corroding first and protecting what matters.

Unfortunately, most shaft zincs and expensive Max-Prop zincs are designed such that the screws used to attach or clamp the zincs are located near the perimeter of the anode, surrounded by a relatively thin layer of zinc. When the edge of the sacrificial metal is eaten away, there’s nothing remaining to hold the zinc in place.

When I worked as a professional diver, I replaced many zincs when the screws were exposed, but when there was still plenty of material remaining to protect the hardware that needed protecting.

Then San Diego diver Van Johnson showed me a trick. Before attaching a shaft or prop zinc, paint a 1-centimeter stripe of nail polish on the zinc adjacent to the screw socket. The paint prevents just that surface area of the anode from dissolving, extending the effective lifespan of the zinc, thereby preventing waste and saving money. And remember, don’t sink or dump used zincs; recycle them. Many marinas have collection sites for used anodes.