There are friendlier alternatives to zinc anodes.
Electronics are always exciting, engines can E be a thrill, even mooring lines and anchors catch passing glances in the chandlery. But let’s be honest, most boaties don’t give a second thought to their sacrificial anodes – those curious knobs of raw metal found on outdrives, shafts, rudders and other metal components that dangle under a boat.
We know that the anodes protect those important metal bits from corrosion, and we know that over time they will wear away and need to be replaced. But beyond that, no one ever gives them a second thought.
That’s too bad, because anodes are actually pretty amazing things. Metal parts that remain submerged under the water tend to corrode quickly as a result of naturally-occurring electrochemical reactions. Anodes are made from special metal alloys that have a particularly attractive electro-chemical voltage range, causing these corrosive reactions to focus on the anode instead of the adjacent metal components.
The principle is a bit like catering for a kid’s birthday party by serving cake and broccoli at the same time – the cake gets devoured while the broccoli escapes untouched. It’s a simple approach that works equally well on small boats, large yachts,
We have to let people know there are alternatives to zinc that are safer to use...
commercial ships and even shoreline installations like sea walls and lock gates.
Anodes have historically been made from zinc-based alloys – to the point where they’re more commonly known as ‘zincs’ than by their proper name. While zinc is an effective anode material, in recent years its use has come under the microscope in light of mounting evidence that the stuff causes real problems when found in high concentrations, such as in the water around marinas.
In the US, water testing in the vicinity of large marina facilities in California, Washington and Delaware has consistently yielded samples showing significant levels of zinc. What’s concerning is that while small amounts of zinc are considered essential for human health, new research suggests that exposure to high concentrations of it could be linked to a variety of serious health concerns. That contention is supported by a growing body of evidence indicating that prolonged exposure to high levels of zinc is toxic to a wide range of aquatic plants, invertebrates and fish.
What’s worse, zinc anodes frequently contain additives like cadmium, an element that has been conclusively associated with serious illnesses including kidney disease, atherosclerosis, hypertension and cardiovascular diseases. Cadmium has also
LEFT Zinc anodes can cause environmental damage when present in large numbers, such as in marinas. Aluminium or magnesium anodes are kinder to marine life.
BELOW & BOTTOM LEFT They do their job well, sacrificing themselves for the good of your boat. But there are alternatives to zinc anodes.