# Advice on aluminium corrosion.



## alexanderfitu (Jan 4, 2015)

Hi all

My 2003 CL55 has corrosion in various places.

The worst is the bonnet and the C pillar:

   

Whist I appreciate this will require re-painting, I do not think I will be able to get a good colour match in a DIY manner on a silver car....

It has gotten twice as bad in roughly 2 years.

I wonder, is there anything I can do to prevent the spread of the corrosion until I can get the whole car resprayed? I was thinking of trying to get Dynax rust proofing into the cavity on the C pillar.

The rear arches I can probably repair myself, they haven't gone too far round, so a bumper off job could probably keep them at bay and look ok. That said, the sunroof also has some spots and is causing water ingress into the car around the seal....

Any advice would be much appreciated.

Many thanks


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## Vossman (Aug 5, 2010)

The problem with corrosion in aluminum is that the bubbling is caused by gas bubbles in the metal, you may keep it at bay for a while but you will never get rid unless you change the complete panel for new a one, I know this is not practical with some parts of the car, the same goes for alloy wheels with corrosion, if they are powder coated the heat of baking the powder brings the gas bubbles to the surface under the coating, it wont break the surface of the coating but it does look bad, wet spraying will make it look very smooth and finished but it doesn't last long before the corrosion appears again. 
Probably not what you want to hear but replacement of panels or parts is the only real answer to the problem with aluminum.


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## alexanderfitu (Jan 4, 2015)

Thanks. 

I have spoken with another 215 owner that had all his corrosion repaired 8 years ago and has not had it resurface since. He had it in the same place as mine. 

I understand that the C pillar corrosion is caused by galvanic reaction between steel C pillar structure and the aluminium rear quarter, is that not the case in these pictures?

If its the case, as you say, then its terminal and un repairable?


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## Vossman (Aug 5, 2010)

Where alloy meets steel will always be a vulnerable area, it is difficult to repair but easy to sand down, fill and paint, it will come back in time no matter what product you use to try and hold it back, aluminum is a brilliant material but just vulnerable where it meets steel. 
I can't give you any advice on what to do in your case, it all depends how much you value your car and what it means to you, do you have a short job done just to sell the car on or do you spend a good amount to have a proper repair done to keep the car?


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## alexanderfitu (Jan 4, 2015)

Vossman said:


> Where alloy meets steel will always be a vulnerable area, it is difficult to repair but easy to sand down, fill and paint, it will come back in time no matter what product you use to try and hold it back, aluminum is a brilliant material but just vulnerable where it meets steel.
> I can't give you any advice on what to do in your case, it all depends how much you value your car and what it means to you, do you have a short job done just to sell the car on or do you spend a good amount to have a proper repair done to keep the car?


I will be keeping the car for the foreseeable future (having just bought it back from my mechanic . Happy to spent reasonable money to get it back to new condition.

It would appear that a repair has been done on the drivers side C pillar already. The passenger side is not showing any corrosion, so appears to have been done to a higher standard!

When I had the car, it was garaged for 3 years and the corrosion did not get any worse. In the last 8 months it has been stored outside and its has approximately doubled in size.


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## Vossman (Aug 5, 2010)

A good body shop should be able to help you with it then, go for one that is recommended by someone on the Merc forum, there are some good people on there and you won't go far wrong, it will soon look like it should again :thumb:


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## alexanderfitu (Jan 4, 2015)

Any thoughts on slowing it down. Dont have the budget for a full respray on the good side of this year, would hate it to become a scabby mess in the winter...


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## Simonrev (Nov 26, 2012)

Probably good idea to search on the land rover forums as this corrosion is common ... I seem to remember reading somewhere that you can treat it with acid but may be totally wrong ... also if it is the reaction between steel and aluminium the land rover way was to try and separate these areas with fixings that used rubber washers of some description ... to stop the two materials touching.


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## alexanderfitu (Jan 4, 2015)

Simonrev said:


> Probably good idea to search on the land rover forums as this corrosion is common ... I seem to remember reading somewhere that you can treat it with acid but may be totally wrong ... also if it is the reaction between steel and aluminium the land rover way was to try and separate these areas with fixings that used rubber washers of some description ... to stop the two materials touching.


Good shout! Thanks.


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