Noticed that there is bubbling under some of the paint on the left-hand door of my "new" 1986 "90". Now I thought they were aluminium on a steel frame as my S111 is, so what is causing the ally rust and how do I cure it? No salt around here.
Can I get the grey colour, "slate", in spray cans?
The steel frame is causing the aluminium to corrode. It's an electrolytic effect. Salt will make it worse but it gets by without any.
David
It seems to be on the outside of the door though, not near the frame which is on the inside. So what do I do about it? No sign of anything like this on my S111 which is 12 years older, did they downgrade their painting procedure, change the quality of metal, or something?
Common problem I'm afraid. If it's very bad but the frame is ok then it may be worth reskinning the door.
Steve. Suffolk. remove 'knujon' to e-mail
On or around Fri, 2 Jan 2004 23:46:45 -0000, "Bob Hobden" enlightened us thusly:
could be. hard to tell. Technically, when assembling alloy panels to a steel frame, you should (electrically) insulate 'em to prevent this. Of course, they don't.
It's a not-uncommon problem all over land rovers.
Austin Shackles wrote in news: snipped-for-privacy@4ax.com:
But aren't oxygen and water part of the equation?
I have the same problem (or rather my LR does though it often feels like it is ME who is affected!). I am thinking of welding triagular plates in the lower corners of the frame (which are cracked), then treating the rust with something like Jenolite. Then etch to remove aluminium oxide, a good rinse down, dry, then coat with a proprietory sealer paint, finally prime, plastic padding, and finish. Whether it will work, of course, is another matter but in theory that ought to stop the corrosion...shouldn't it??? If it is dry and the air is excluded, can electrolytic action still occur?
Derry
Derry Argue wrote: (snip) If it is dry and the air is
No. Electrolytic corrosion can only occur in the presence of water, and with two dissimilar metals in electrical contact in the same solution. (pure water = no corrosion - but where will you find pure water on a road?) Insulating the two is a useful precaution, stopping the water getting on them is as well. It is usually easier to be sure they are insulated than to be sure the water is excluded - if it is done at the design stage. In this case the corrosion may have started because of impurities in the aluminium, and poor quality control in the manufacture of the alloy sheathing may possibly be the problem. In this case excluding water is all you can do, except reskin the door. Of course, you also have to exclude air to exclude water, as the air in most places is damp and will condense out water on metal overnight, even if on a microscopic scale in a pore in the paint. JD
On or around 3 Jan 2004 19:06:00 GMT, Derry Argue enlightened us thusly:
yebbut, you've *always* got them in this country at least.
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