Dreaded rust / tin worm

Discussion in 'Motorhome Chat' started by Mattyjwr, Jun 8, 2016.

  1. Mattyjwr

    Mattyjwr Funster Life Member

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    Both of our vehicles are showing signs of rust - the Mazda Bongo more extensive than the Merc. Both are nearly 20 years old.

    I've cut back the worst of the rust on the Bongo and started the anti-rust treatment. The Merc has seen the side of the flappy pad from my angle grinder as I've stripped the paint back on the side of the arches facing the wheels as it was bubbling and showing rust.

    I've treated some of the exposed metal with Hammerite rust removing gel - which I don't like as it leaves a thin film over the surface of the metal which I do not think is good to paint over.

    The rest of the metal has been treated with Jenolite stage 1.

    Hoping that I have killed the rust, should I use Hammerite anti-rust primer and then paint / spray over the top or use Jenolite stage 2 before painting? I've used Jenolite before but read some reviews recently saying that that film it puts over the metal is great for keeping damp out but it is also good for hiding rust that can develop underneath it so all looks fine until it more damage has developed.

    What rust treatment do you use and what top coat do you recommend once the primer has been applied?
     
  2. Dave K

    Dave K Funster

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    I've had a couple of VW T4's in the past which always suffered with rust around the arches, only way to get rid of it is to cut it out and renew sections, depending on budget of course, anything else just seems to be temporary
     
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  3. Mattyjwr

    Mattyjwr Funster Life Member

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    It is frustrating how temporary repairs can be. I can't work out how some areas can rust without any apparent damage to the paintwork when the rear of the panel is sealed or protected from rain / spray.

    It was disappointing to see how many small areas of rust were developing on the Merc but I only noticed it because I wash my vehicles by hand to help check for such deterioration.
     
  4. Dave K

    Dave K Funster

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    I've been there myself Matt, always washed the T4's by hand and even after getting one resprayed and treated professionally it was showing signs of coming back within 12 - 18 months, as you said previously it can rust towards the inside even if you try and seal the outside, long term the only way is to cut out and replace.
     
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  5. Charlie

    Charlie Funster

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    I think it's in the steel or the quality of the steel. We woul associate materials used in quality brands as being of a high quality but it's not always the case. If the actual steel is not great it will fail and especially in the more exposed or prone areas. I'm no metallurgist but that's maybe what it is .
     
  6. Mattyjwr

    Mattyjwr Funster Life Member

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    I understand that road salt has become more corrosive and less refined (no longer rounded but as angular as it is mined) so not only is it more likely to cause paint damage but the corrosion is more severe.

    I'll treat this again as well as I can, but keep an even closer eye on the areas treated to monitor the effectiveness of the poor ducts that I use.
     
  7. busby

    busby Funster

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    Mercs from 1999 to 2003 are very prone to rust,,,,cheap steel,,,BUSBY.
     
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  8. Wildbill

    Wildbill Funster

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    I have only ever had old vehicles so know where your coming from I cut back and patch then clean till bright with grinding
    disk this gives a rugh finis treet with a zinc based primer then finish with good quality filler not the essay sand crap
    I usually mix in a bit of liquid resin this helps to get a good bond with the repair then use a high build primer then top coat
    I then treat any areas with a mix of under seal and wax oil
    Bill
     
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  9. ambulancekidd

    ambulancekidd Funster

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    When our old Bongo was professionally treated for rust & resprayed, our coach builder informed us that rust tends to start from the inside. So he treated both sides of the metal & we never saw rust on the old girl again. The old girl was white & I always feel that white rusts or at least shows rust before other colours would.s with interest. Our current vehicle which is a Sprinter is beginning to show signs of the dreaded tin worm where there are a few stone chips, so I'll keep watching your post

    Here is the after photo, sorry didn't have before photo.
    [​IMG]
     
    Last edited: Jun 9, 2016
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  10. Geo

    Geo Trader - Funster

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    Rust a comprehensive lesson
    As a guy who cut his teeth on welding and vehicle restoration Ill give you free of charge the benefit of my many years experience, provided you send the mandatory one guinea to Super Mike who's funds must be getting a bit low now, as we don't see so much of him these days and he has been kind to me "the ole spanner man" of late.

    Preparation as always is important but not the key with respect to rust and corrosion
    Corrosion is not a virus it can not spread like a virus,:)
    It is the simple result of a chemical reaction. and contrary to popular belief its not contagious either, although to be brutally honest there some vehicle I wont park next too just in case;)
    Some one said it's in the metal, well that,s almost right some of the chemicals are that,s for sure, there are metals more prone to rust than others you can realistically call those cheap metals because the more rust resistance the dearer they cost right up to high grade stainless
    So what is the key to halting rust ? its very simple really, just like a fire there are 3 elements required to make it go wild
    In a fire its a combustible material, a heat source and oxygen, remove any one of those and a fire is unlikely remove any two and its virtually impossible to make a fire
    In rust you need Steel, damp and oxygen and yet again remove any one and rust is rare remove any two and it cant happen
    So lets go for the easy method first,
    1. get rid of the steel = No vehicle = no rust that's called the 100% method
    Next easiest are 2 and 3 together,"The Key"
    Treat what rust you have with a rust converter such as jenolite, a long standing proven (acid) based product and then prime, as I said earlier preparation as you have read is not as important as depriving the rust of what it craves. (read on)
    then as bill has aid using quality restoration fillers, aluminium based for example but most importantly water proof resins and such fillers are best, the easy sand stuff is easy for a reason it's simply extremely porous 95%+ chalk powder bulk cheap fast trade bodge it and run filler
    Please note once filled and sanded it should be painted asap and Primer is NOT water proof but will keep 1 of the ingredients away (oxygen)and that's were many attempts fail, as its left and lets in microscopic damp and the other magic ingredient oxygen, and as we all now know that along with the steel, that all adds up once again to rust and a failed repair
    So you really do need good dry days preferably in doors too to starve the cocktail of it's two main ingrediant until the sealed finish coat is applied just like it appears the Bongo was done (y)
    and that means both sides of the corroded area , if any part of it can not be sealed even resorting to drilling and waxoil if that is the only way, but if even that is not possible as is the case sometimes, then be prepared to just slow it down and not cure it.
    Cutting out and welding in new steel is not a cure either unless as already stated 100% of the new metal and weld can be seal both sides, this is just another slow down exercise
    I sincerely hope you now have an honest understanding of rust and corrosion and the difficulty in curing it even for the "Experts out there.
    My favorite saying was "Well if they couldn't get it right at the factory what chance do i have now its assembled":doh:

    Geo
     
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  11. Mattyjwr

    Mattyjwr Funster Life Member

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    Ours is 1996/7 - I hope that it is better metal than the later ones - it seems to be lasting longer than many that I have seen from the early 2000s but I want ours to last for much longer so am hitting every rust spot I can find ASAP.
     
  12. Mattyjwr

    Mattyjwr Funster Life Member

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    @Willdbill - what do you mix the liquid resin with, what primer to do you use and what filler do you use?

    Many thanks for this info @Geo . I am trying to deprive the metal of humidity / water but some areas of rust are impossible to get behind, as you have mentioned so surface treatment will have to surfice until the rust comes through again and I can confirm that the rust was not initiated by stone chips etc.

    What aluminium filler do you recommend? I was about to use Isopon 38 but I've read some reviews suggesting that Upol Easy sand is better. However, both are are regarded as easy sand. I don't mind working a bit harder if a different filler is more effective but not so easy to sand. Do you think that Davids ISOPON Metalik Paste would be OK? http://www.halfords.com/motoring/pa...preparation/davids-isopon-metalik-paste-250ml or this http://www.halfords.com/motoring/pa...reparation/u-pol-extra-polyester-filler-600ml

     
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  13. Wildbill

    Wildbill Funster

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  14. unimog

    unimog Funster

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  15. Mattyjwr

    Mattyjwr Funster Life Member

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    Thanks @Willdbill . I used to think that Halfords was a complete rip-off too but I went there with a voucher that I had been given from colleagues and found a number of things that I needed. When I compared the prices to online suppliers, everything that I wanted was cheaper in Halford's store than off Amazon or other online stores.
     
    Last edited: Jun 10, 2016
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