Electrolytic corrosion
I READ with interest various articles in Land Rover Monthly regarding repairs to aluminium panels that have crumbled away where they have been up against steel structure at doors, load bay floors, inner wing mud panels, etc.
The cause is electrolytic corrosion, the difference electrically between the steel and the aluminium, and it acts in a similar way to a battery or plating process. It involves very small voltages but is greatly increased in damp or salty damp conditions, conditions often found under Land Rovers.
To prevent this a barrier needs to be applied between the two materials. This was appreciated by Rover who galvanised a lot of the steel used in Land Rover bodies. The galvanised zinc coating forms a barrier greatly cutting down the corrosion. Cost cutting in the 1980s saw the galvanising replaced by powder coating that in theory also acts as a barrier, but in practice is nothing like as hard-wearing and leads to rusty cappings and corroded panels.
Having spent some time working in and around buses that also contain large amounts of steel and aluminium with exactly the same issues, I’m surprised that the Land Rover community has not adopted the same solution as many coach-building companies in using a brush-on Dialectic jointing compound. Whilst normal paint is no use whatsoever, a purposemade jointing compound effectively prevents the corrosion between the two materials and can be painted over once dry. I used a compound called Duralac when re-making doors for a Lightweight some years ago (wish I still had it now!) and rebuilding the front panels.
One note of caution, from experience, this yellow jointing compound, which is like a thick paint, seems to have a mind of its own and if one isn’t careful it gets everywhere, so if anyone decides to try it, wear gloves and overalls. It’s available from several sources on the internet and very easy to apply with a brush – apply one coat on each surface and let it dry before assembling.
I have also applied it when using stainless steel components against steel where similar issues can arise, depending on the type of stainless steel.
I hope this information may make some people’s restorations a little easier – better but possibly a bit messy. George Luke