Sacrificial aluminium anodes for boats are specifically designed to protect those metal parts submerged and exposed in water and, unlike a traditional zinc anode, is completely calcium-free.
Boat Hut provides a wide range of quality Martyr anodes including a zinc anode and round models to suit propeller shafts and rudders, block models for hull protection, complete kits for stern drives, outboards plus pencil models for diesel applications and other applications (e.g. heat exchanger).
In recognition of our delicate marine environment, Boat Hut introduces a range of pressure die-cast Martyr aluminium anodes for boats (Mil A 24779 SH). Where traditional zinc anodes use small amounts of Cadmium in the manufacturing process, all Martyr aluminium anodes are completely Cadmium free, being predominantly made of non-toxic aluminium and Indium.
The Cadmium free anode offers many benefits and advantages over the traditional zinc type.
In addition to being more environmentally friendly, the aluminium anode is significantly lighter for the same given volume, which can result in fuel savings where large zinc block anodes have previously been used.
Martyr aluminium anodes offer improved performance and efficiency due to its electrical capacity to become sacrificial, being almost twice that of zinc, weight for weight. This electrical advantage results in longer anode life of up to 50% over zinc whilst providing excellent corrosion protection and benefiting the user by extending time between anode replacement.
The following is a brief technical comparison between zinc and aluminium anodes. Look for the dedicated aluminium anode code listed within the tables, if available.
Zinc capacity of ampere hours per 453 grams is 355 hours while aluminium is 1225 hours
• A zinc anode will give one amp for 355 hours for every 453 grams of zinc while aluminium will give one amp for 1225 hours per 453 grams of aluminium
• A typical 4.68kg zinc anode performing at 0.5 amp would be expected to provide 7312 hours (10 months) of protection
• Typical same sized 2.7kg aluminium anode performing at 0.5 amp would be expected to provide 12,250 hours (16 months) of protection Aluminium features and benefits include:
• Environmentally friendly, cadmium free
• Lighter weight for given volume than traditional zinc anodes
• Improved efficiency resulting in longer service life
• Less weight for better fuel efficiency
• Wide range available including stern drive kits
Anode Selection Guide
Hull Material Wood Fibreglass Alum Steel All
Freshwater (Pure) Alum Alum Alum Alum Alum
Freshwater (Polluted) Alum Alum Alum Alum Alum
Brackish Alum/Zinc Alum/Zinc Alum/Zinc Alum/Zinc Alum
Saltwater Alum/Zinc Alum/Zinc Alum/Zinc Alum/Zinc Alum
Without proper protection, your boat and motor can be ruined by galvanic corrosion, as a result of electrolysis.
A boat may have many metals electrically connected in a saltwater solution (the sea). When two dissimilar metals are electrically connected and submerged in an electrolyte (seawater) a natural chemical reaction takes place. This chemical reaction forms a circuit where the least noble metal – the anode – will begin to break down leaving the most noble metal – the cathode – (e.g. the motor leg) intact.
The lower leg of an outboard motor or stern drive for example needs to be
protected by anodes. The anode will be sacrificed leaving the lower leg protected.
Anodes can also provide low cost cathodic protection on ocean-going vessels, structures and equipment constructed of steel and other metals.
Anodes are manufactured from high grade zinc (99.995%) and are alloyed to conform to US mil spec MIL-A-18001K aluminium/zinc composition,
(designation Z1) and subject to strict quality control.
What are Sacrificial Anodes?
Sacrificial Anodes are highly active metals that are deployed to prevent a less active material surface from being corroded. Sacrificial Anodes are made from a metal alloy with a more negative electrochemical potential than the other material/metal it is intended to protect. The sacrificial anode will be consumed in place of the metal it is protecting, this is why it is referred to as a sacrificial anode. Sacrificial Anodes are used to protect the boat hulls, water heaters, heat exchangers, marine engines, pipelines, distribution systems, above-ground tanks, underground tanks, and refineries. The anode in a sacrificial anode cathodic protection system must be periodically inspected and replaced when consumed.