Looking at buying a 560SEC and bodywork is generally v good apart from a small circular area, about 2 inches across, surrounding both windscreen washer jets. Here the paintwork is bubbling slightly. I am told that it can't be rust as the bonnet is not steel (?!). In which case what is it and how do you fix it? Comments and advice much appreciated.
Anders
Active Member
I am almost 100 % certain that it is steel, so would suspect that it is good ol' MB tinworm...
jeffreyli86
Active Member
I'm with Anders. My dad used to own one of those and it rusted at the same place too... However we had ours long long ago when I was a kid... At least 10 years ago.. So if yours had just developed the rust, it must've been quite carefully looked after..
Steve_Perry
MB Enthusiast
Shouldn't be but if previous owners use dish washing detergent (e.g. Fairy Liquid) as a stop gap then that will really accelerate rust as it contains sodium salts.Shude said:
S.
Brian WH
MB Enthusiast
Steve_Perry said:
Or Antifreeze neat.
Satch
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Steve_Perry said:
And, sadly, Chloride ions are really bad news for Aluminium as well. Get a salty solution trapped in a crevice
and that can be quite ugly.
Aluminium may not rust but waiting to strike some car makers is Aluminium corrosion, particularly galvanic corrosion where short cuts have been taken and Aluminium body parts are either left untreated or are not "insulated" from steel or indeed any other metal which is more "noble" that Aluminium.
Satch
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Will they never learn? I understand that Ford and some other volume makers at some point took the view that since the average life of a car is 10 years or 150,000 miles they could get away with untreated aluminium alloy parts, especially in the suspension and underbody, since any significant problems were very unlikely to develop during warranty and the vehicle would be on the scrap heap (sorry, being recycled) before failure.
Aluminium corrodes very quickly (actually much more quickly than iron and steel) but the oxide that forms does not fall off like the rust on iron. A hard layer of Aluminium Oxide protects the Aluminium metal beneath.
But when salt is added to the water, Cholrine ions attack the aluminium oxide coating and expose new aluminium metal. As soon as this Aluminium metal corrodes into Aluminium Oxide, it too is stripped from the surface by the Chlorine ions. The natural protection that aluminium gets from its oxide coating is lost, so underbody parts made of untreated or unpainted alloys will often corrode quickly if exposed to road salt. Even if it is not structural, soon looks bad and they presto, spate of warranty claims from unhappy customers in those parts where road salt is used. And all that they saved was the price of a coat of paint.
Galvanic corrosion is simply unforgivable: it has been known about since the 1940's and requires nothing more than a bit of care in design and choice of materials. Of all vehicles, the Land Rover Defender and Discovery of no great age are suffering badly because for some time they had a stupid, stupid, mix of Aluminium door skins over steel frames relying on a rubber based adhesive compound to keep the two apart!
.
Aluminium corrodes very quickly (actually much more quickly than iron and steel) but the oxide that forms does not fall off like the rust on iron. A hard layer of Aluminium Oxide protects the Aluminium metal beneath.
But when salt is added to the water, Cholrine ions attack the aluminium oxide coating and expose new aluminium metal. As soon as this Aluminium metal corrodes into Aluminium Oxide, it too is stripped from the surface by the Chlorine ions. The natural protection that aluminium gets from its oxide coating is lost, so underbody parts made of untreated or unpainted alloys will often corrode quickly if exposed to road salt. Even if it is not structural, soon looks bad and they presto, spate of warranty claims from unhappy customers in those parts where road salt is used. And all that they saved was the price of a coat of paint.
Galvanic corrosion is simply unforgivable: it has been known about since the 1940's and requires nothing more than a bit of care in design and choice of materials. Of all vehicles, the Land Rover Defender and Discovery of no great age are suffering badly because for some time they had a stupid, stupid, mix of Aluminium door skins over steel frames relying on a rubber based adhesive compound to keep the two apart!
.
