Is it possible to set up sacrificial anodes to protect the bodywork of aluminium landrovers ? The question has come up in alt.fan.landrover, but no-one has any idea if its possible to implement it on a vehicle.
Steve: Try searching on Google using the phrase "cathodic protection of aluminum"(and aluminium).
Cathodic protection was applied to aluminum alloys over forty years ago. See:
which references NACE Recommended Practice 2M363.
The galvanic series for metals in soils:
and the series in flowing sea water:
both show that either magnesium or zinc are even more active than aluminum and could be used as sacrificial anodes. In fact you can buy zinc anodes designed specifically for mounting on ships. See:
Unfortunately, automotive cathodic protection is a fatally flawed concept, since you don't have a good way to protect the surface unless you almost completely coat it (which is what is done with zinc on auto body steel panels). See:
The article referenced on the above site by the late Harry Webster gleefully pointed out that orders of magnitude more current went into the LED plot light on one device than went into protecting the car. (Harry had been president of the National Association of Corrosion Engineers and was an expert on cathodic protection. He testified as an expert for the government in court in Ontario).
One product, Rust Evader, also got taken down by the U.S. government. See:
they went offshore to Singapore, and, if you wish to :) , you can still buy one on eBay.
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Landies aren't aluminium - they're mainly steel, with a few bits of aluminium / magnesium alloy bodywork stuck on the top. For something like a Rangie there's a third intermediate layer of a thin steel bodyshell, between the heavy-gauge steel chassis and the aluminium panels.
Corrosion protection for them is simple - use a factory galvanised chassis. That's the part that fails expensively, that's the way to protect it. For the common but replaceable failures (Rangie tailgate frames, Landie doortops) then some form of paint-time zinc coating is worth putting effort into, whether this is just a good zinc-rich primer (like Davids 182) or even a metal-spraying process.
The "aluminium" bodywork doesn't suffer from corrosion - largely because of the alloy used. Although this Birmabright alloy was chosen for strategic reasons post-war (early Landies were literally made from old Spitfires) and it was retained because of its stiffness, it's also a good choice for corrosion resistance.
Zinc anodes, active protection systems etc. are fine, but you have to dunk the vehicle in an electrolyte to really show any benefit. Good for boats, bad for cars.