Anodes are the cheapest insurance on your boat and the most commonly botched. The theory is simple — a sacrificial metal corrodes so your propeller, shaft and gear leg don’t — but three practical rules do most of the work.

Rule one: match the material to the water. Zinc is the traditional choice and works well in clean salt water — but it passivates (grows an inert crust and stops working) in brackish or fresh water. That matters here: river moorings, estuary marinas and rainy-season run-off around Thailand’s coast are brackish more often than owners think. Aluminium anodes protect in both salt and brackish water, run roughly a third lighter, and typically last longer — which is why they’re now the default recommendation for most boats in our waters. Magnesium is for fresh water only; you’ll rarely need it here.

MG Duff zinc hull anode, 2.1 kg pear type — An MG Duff zinc hull anode — cast in their own UK foundry, every batch alloy-tested. Zinc for clean salt water; choose aluminium where the water turns brackish.

Rule two: replace at 50%. An anode that’s half gone has lost far more than half its protection — the remaining surface area can’t pass enough current to cover the metal it’s guarding. Check anodes at every haul-out (annually at minimum in the tropics; growth and warm water accelerate everything), and replace anything past half worn. They’re consumables, like engine oil — being proud of an old anode is being proud of a worn-out one.

Rule three: never paint an anode, and fit it to bright metal. Antifoul or primer on an anode switches it off completely. Fit anodes to clean, unpainted metal, tighten them properly (a loose anode protects nothing), and if your boat has a bonding system, make sure it’s actually connected — a broken bonding wire quietly disconnects half the protection on the boat.

Sterndrives deserve a special mention. A sterndrive leg is an aluminium casting living next to a stainless propeller — the most galvanically exposed metal on your boat. Use the drive-specific anode kit for your leg (generic anodes don’t sit on the machined contact points) and check them mid-season, not just at haul-out.

We stock MG Duff zinc and aluminium anodes — cast in their own UK foundry since 1956, every batch alloy-tested, zinc to US MIL-A-18001K spec — in hull, shaft, disc and drive-specific patterns.

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