Bubbling on the bodywork

Discussion in 'Tech/Mech General' started by DavidEJM, Nov 1, 2009.

  1. DavidEJM

    DavidEJM Read Only Funster

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    Over the past 12 months or so the stripe on the side of our Compass Drifter has started to bubble in places. Now usually (in my experience with old cars) this points to rust, but of course the side of the van is aluminium.

    I have peeled the sticker back and sure enough there is a dry powder (oxidisation) behind and a small hole in each instance through which I can see the insulating foam.

    Anyone have any thoughts on the cause? (not there when we bought the van and the stripe appears to be original) and what is the best way to repair?

    I'm reasonably competant having worked on car bodywork up to the point of restoring and respraying cars, but never with aluminium. I know of products that you can use to effectively weld ali (blow torch on screwdriver blade, 'tin' the screwdriver with product and wipe over hole..........one of those things you see at shows, get home and find that it takes years of practice to use effectively) and I might take this route. Or does someone have a better (for which read simpler) idea?

    And finally...... what is the thought on striping? keep it original or do your own thing? Will this have any effect on resale values (keeping things looking original)

    Well hope that makes sense and thanks in advance.
     
  2. Tony Santara

    Tony Santara Funster

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    I would choose the easy option ....clean up the affected area by sanding and fill the hole with P40 body filler take it down smooth with wet & dry sanding paper spray it with primer and restripe over it.

    As for striping I did my own thing on my old Winnebago not to original but my own design made for me and applied by my local vynil sign maker it didn't affect the sale of it later made it more individual :Cool:

    Good luck :thumb:
     
  3. Johns_Cross_Motorhomes

    Johns_Cross_Motorhomes Trader - Motorhome & Accessory Sales

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    Clean the corrosion out thoroughly and fill with plastic padding or similiar, rub down until smooth and get a new stripe made from a local signwriter (get two, one for the other side to colour match)

    Use fairy liquid in water to allow the new stripe to slip into position you want and rub out any air bubbles with a cloth.

    Peter
     
  4. Terry

    Terry Funster

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    Hi David you have already identified your problem as -tin worm- It will be almost impossible to weld leaving you the option of filling etc or replace the full sheet :Eeek::Eeek:
    Personally I think it will keep coming back every few months :Eeek: chances are it will have come from the inside out :Eek!::Eek!: Since normal vans are only .5 mm thick ali one hole will lead to another,not what you want to hear :cry: Look seriously at getting rid :thumb:
    Drastic I know BUT
    terry
     
  5. hilldweller

    hilldweller Funster Life Member

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    I'd pick a convenient hole and peel it back to find out why ? If it's damp from behind you need to know now.

    Or was it a hole in the original stripe ? Maybe someone pricked it to get rid of a bubble. ?
     
  6. DESCO

    DESCO Read Only Funster

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    Had similar on first motorhome years ago, did as terry advises and got rid ASAP.



    Dave:thumb::thumb:
     
  7. pappajohn

    pappajohn Funster Life Member

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    i'm inclined to agree with Brian.

    a shoddily applied sticker and its been pricked to get rid of the air bubbles.

    the "pin" has probably also pierced the protective coat on the ally skin and allowed water in.
     
  8. metz

    metz Read Only Funster

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    Hi, Sounds like osmosis to me, usually caused by damp reacting with the adhesive used to bond the Ally to the insulation, or the Ally is in contact with a dissimilar metal, sand down clean up fill and refinish is just about your only option, needs checking for damp though, and if any found, the problem area repairing.
     
  9. DavidEJM

    DavidEJM Read Only Funster

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    mmmm, thanks all.

    Some worrying comments there, can't really afford to get rid at the moment so will have to effect some repairs. Looks like I will be having a busy winter!

    The affected areas are very localised (small holes generally) and seem to match the suggested badly applied sticker (or more likely that is the answer i want:Smile:) Not sure how damp from behind could be the cause because there is foam directly behind these areas with no evidence of damp there.

    I will carry out a more detailed inspection over the next few days and see if a cause can be found, because that is now my main concern.

    So, whilst you’ve put the wind up me............... thanks.
     
  10. Douglas

    Douglas Read Only Funster

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    Aluminium corrosion once started is very difficult to control, on aircraft the affected area is mechanically cleaned until there is no pitting visible with a high powered magnifying glass, a jewelers loop or similar.

    After this the area is treated with Chromic acid or paint containing chromic acid (Etching paint) and then a top coat if the area is external.

    In your case this kind of treatment is going to be difficult as you can not get at both sides of the metal and it is to thin for this method.

    It is certain that covering the area is not going to stop the corrosion, it will continue underneath anything you cover it with. all be it very slowly.

    On an aircraft the effected area would be cut away and a new section of identical metal would be riveted as a patch. this is also would be very difficult for you as you don't have access to both sides of the metal.

    I would think that the application of chromic acid or etching paint containing chromic acid is your best way of treating it but I do not know what effect the acid would have in the foam insulation that will be on the inside of the aluminium skin.

    http://www.ashton-moore.co.uk/scope_approvals.htm
    http://www.finishing.com/1200-1399/1318.shtml
    http://www.pfonline.com/articles/pfd0002.html
    http://www.spcb.co.uk/acatalog/Etching_and_Degreasing_Aluminium.html

    Doug...
     
    Last edited: Nov 3, 2009
  11. Landy lover

    Landy lover Funster

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    Totally agree Doug

    Thiis is exactly what we do with Land Rovers that suffer with the same problem - we find it does a pretty good job and can last a considerable number of years - once the white powder has been removed and the surface roughed up with wet and dry we clean with a clean lint free rag with a small amount of cellulose thinners on it - allow to dry and then spray or if a very small area with and artists brush. We then paint as normal. Always worth checking compatability of paint systems first though. Most good commercial paint suppliers can advise on this though.
     
  12. DavidEJM

    DavidEJM Read Only Funster

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    All great advice chaps, I knew I should have asked about this sooner!!

    Just had a scrape at one of the bubbles and the 'infliction' seems to be going from the outside in, as the ali is not perforated (yet) just lightly pitted. I will get some of this etching paint, get the dremel out, and go for the repair.

    I will take some photos and show the steps I take, you can then stop me if I've done something wrong or it may be useful to others with the same problem.

    David
     
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