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Sealing Porous Magnesium Alloy Wheels?

Discussion in 'Technical Q&A' started by dave80gtsi, Mar 30, 2005.

  1. dave80gtsi

    dave80gtsi Formula 3
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    Does anyone have any tips or tricks to ensure the proper air sealing of older porous magnesium alloys?

    I checked the air pressure in my early 14" spare wheel / tire several months ago, and it was dead flat. Upon reinflation, spraying a soapy water mist onto the wheel revealed that there were several small air leaks through the side wall of the wheel itself, unrelated to the tire mounting perimeter or to the valve inflation stem. This, in spite of the fact that I had just silver powder coated the rim, including the interior portion inside the tire, last year.

    So, I had the tire removed to inspect the interior of the rim. No sign whatsoever of any cracks, holes, gaps or problems in the powder coating around the location of the leaks. Even so, I sprayed the inside of the rim all around with several coats of silver rattle can enamel to act as an additional rim sealer, and then had the tire remounted and rebalanced.

    I now discover that, while the air leak does seem to be improved, it is still seeping at the same locations.

    The only idea that now comes to me is to squirt in a can or two of Fix-A-Flat, but that stuff leaves such a gooey residue mess inside of the tire and rim that I am hesitant. Does anyone have any better ideas?

    Cheers - DM
     
  2. don_xvi

    don_xvi F1 Rookie

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    Good call holding off on the Fix-a-flat. It's designed to seal tires, not wheels and will only seal where it's exposed to.

    In the absence of better suggestions, you could try painting the inside with POR15 (por15.com) I'd bet you could sand up that powercoat and make it stick. This stuff might work well for you.
     
  3. staatsof

    staatsof Six Time F1 World Champ
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    I'd try and find out what's really going on with this leak. To do that you need to remove the powdercoating. Perhaps it's porosity or a stress crack? Perhaps from the heat of the powdercoating process. Better to find out with the wheel off of the car.

    This comes at a timely moment for me as I've just had my Magnesium racing wheels bead blasted to repaint them. They are "only" 10 years old but lightly used. I was thinking of powder coating them but was advised against it because you want to be on the constant look out for cracks in racing wheels. So I'm polishing the lip and giving the wheels a light coat of anthracite paint with a zinc chromate primer to prevent mag corrosion.

    I can do this every other year because regular paint removes easily.

    I have an older Campagnolo rim that leaks like yours and I haven't needed it but I suspect that Loctite propbably makes a penetrating product for this situation. Call their Industrial tech help line, they're very good. You have to find the spot that's leaking first.

    Bob S.
     
  4. Smiles

    Smiles Moderator
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    How about radial tire inner tubes, such as ones available from Coker Tire?
     
  5. bill365

    bill365 F1 Rookie

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    If you decide to go that way.... The only radial VR rated tubes I know of, are being distributed by Roger Kraus Racing... Got 5 for my car. They also have the threaded metal valve stems!!

    Bill

    Roger Kraus Racing
    2896 Grove Way
    Castro Valley, CA 94546
    Ph:510-582-5031
    Fax: 510-886-5605
    Orders: 800-510-7223
    info@rogerkrausracing.com
    www.rogerkrausracing.com
     
  6. 8valve

    8valve Formula 3

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    I have been advised NEVER to use inner tubes on a 308. If the rims leak, it's slow. If a tubeless radial tyre goes, in 75% of the times it's slow. If an inner tube goes, it's with a bang. dangerous.
     
  7. bill365

    bill365 F1 Rookie

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    Hi Mick,
    How does a tube that is within a tubeless tire go with a bang, when it can only leak into the tire??

    Regards,
    Bill
     
  8. Smiles

    Smiles Moderator
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    Who gave you this advice?
     
  9. Napolis

    Napolis Three Time F1 World Champ
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    Ditto That.
     
  10. bert308

    bert308 Formula 3
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    When the inner tube is inflated, there will be airbubbles trapped between the inner and outer tire unevenly spread across the tire and at high speed this trapped air can get hot and cause the outer tire to blow. Not sure if this is the exact explanation, but it is something like that.
     
  11. Smiles

    Smiles Moderator
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    There sure are some odd tire theories floating around the Netherlands! :)
     
  12. Darolls

    Darolls F1 Veteran
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    Nope!

    Any "trapped airbubbles" will expel themselves through the hole in the wheel that the valve stem goes through.

    A possibility is excessive heat created due to friction between the tube and tyre; but I've never heard of a problem with that either.

    I debunk the theories but, then again, I may be wrong...........

    Nah...I'm not wrong. :)
     
  13. Philjay50

    Philjay50 Formula Junior

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    Got to put my 2 cents worth in here, over many yaers, too many to count, I have used inner tubes in a variety of cars and never ever had any type of problem ! When I have removed tyres some (tubes) have shown signs of scuffing, but nothing serious. Have them in the alloys on my bmer 02 and in my Stag.
     
  14. vroomgt

    vroomgt Formula 3

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    There is a product which i believe is made by loctite used primarily in aerospace applications.

    Esssentially it is a costituent in a bathing process wherby the wheels are dipped in a bath for a number of hours.

    THE SOLUTION FILLS THE PORES AND CRACKS OF THE MAGNESIUM, AND AFTERWARDS THEY CAN BE PAINTED AS PER USUAL.

    I know Ferrari restorers here who send their wheels away to get this treatment at aircraft maintenece places.
     
  15. bert308

    bert308 Formula 3
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    Didn't realise the valve from an inner tube is non-sealing
    That may be a better explanation. Anyway I know it is not a good idea to maintain 150+ mph for an hour on the German Autobahn with an inner tube in a tire designed to be tubeless.
     
  16. 8valve

    8valve Formula 3

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    A tire specialist here in Amsterdam. I personally have no experience with inner tubes (except on my bicycle, it went with a bang once). A friend of mine had a porous magnesium 14" wheel on his 308, and we were looking around for solutions to get him back on the road. The tire guy advised us urgently not to go the innertube way.
    I was not ventilating my own opinion (since I'm no expert I don't have one) but just passing on what I had been told. Any more insights on this?
    Btw, the wheel turned out to have a hairline crack, close to the bead and in the direction of rotation. I remember another thread where a similar problem was discussed and it may have been caused by the settling of the tire (the loud 'pop') when mounting it....I think there is no economically feasible way to repair these magnesium wheels, is there? The hairline crack was stop-drilled, but the material can't be welded, since it burns.
     
  17. staatsof

    staatsof Six Time F1 World Champ
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    That's what I figured. Do you have a reference on what it's call or the product #. Given that it's a bathing process I guess you have to send it somewhere. Probabnly not cheap so depending on the car a new wheel might be better.

    Bob S.

     
  18. staatsof

    staatsof Six Time F1 World Champ
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    That sort of crack would have me looking for a new wheel. I have spoken with a couple of shops that claim they can weld an Magnesium alloy of the type typically used in these wheels but I haven't tried it. I also don't know if it would reliably fix a crack. Sounds like it's not worth the risk. In my case it was to fix a gouge caused by a careless maintenance shop. I decide to fill it instead.

    Bob S.

     
  19. pete04222

    pete04222 Formula Junior

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    This is just the spare tire isn't it? It's not like you plan on using it, you just want it to have air in it should you ever need to use it.

    I don't think I'd have any problem putting a tube in my spare tire. Another thought I had would be to coat the inside of the rim with epoxy resin. Both of these options would be cheap and easy.

    I think magnesium welding or sending the rim out for an aerospace coating is a little extreme for a tire whose main function is to make the battery harder to get to.

    Just my $0.02
     
  20. Smiles

    Smiles Moderator
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    Well said!

    If, for some reason, a tube sounds unacceptable, people have been using Glyptal enamel for years to seal porous castings, although I've never heard of it tried on magnesium. Besides, sealing air inside a magnesium wheel isn't what Glyptal's really intended for, while an inner tube is.
     
  21. lmpdesigner

    lmpdesigner Formula 3
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    Please see the following:

    http://www.indestructible.co.uk/rockhard/MAGPR2.html

    http://www.thomasregisterdirectory.com/anodizing/military_specification_anodizing_0050301_1.html


    DOW #1
    (Chrome Pickle) MAGNESIUM MIL-M-3171 TYPE I Removes 0.0006 - 0.001 metal
    Gray to brown For temporary corrosion resistance. Affords such protection as may be required during machining, shipment, and storage. My be used as a paint base.
    DOW #7
    (Dichromate Treatment) MAGNESIUM MIL-M-3171 TYPE III No dimension change
    Brassy to dark rown Good paint base. Best corrosion protection of the chemical coatings for magnesium. May be applied to all alloys except EK30A, EK+1A, EZ33A, HK31A, M1A, HM31A, HM21A, and LA141A.
    DOW #9
    (Galvanic Anodize) MAGNESIUM MIL-M-3171 TYPE IV No dimension change
    Dark brown to black Good paint base. Used on alloys that won't take DOW #7 and parts requiring a non-reflective black coating.
    DOW #17
    (Anodize) MAGNESIUM MIL-M-45202
    TYPE I - Light Coating
    CLASS C - Light green coating
    TYPE II - Heavy Coating
    CLASS D - Dark green coating
    TYPE I CLASS C 0.0001 - 0.0005
    Light Green
    TYPE II CLASS D 0.0009 - 0.0016
    Dark Green Machining allowances must be made. Good paint base and corrosion protection. Hard non-conductive coating. Castings should be picked, prior to machining, to remove scale and insure uniformity of the coating. The coating thickness is approximately 40% penetration and 60% buildup.
    DOW #19
    (Chromic Acid Touch Up) MAGNESIUM MIL-M-3171 TYPE VI No dimensional change
    Brassy to Brown Commonly used to touch up rack marks, surface scratches, reworked areas, and surfaces that have been remachined or abraded.
    DOW # 21
    (Ferric Nitrate Bright Pickle) MAGNESIUM NONE Removes metal
    Satin to Bright Good paint base. Poor corrosion resistance. May be coated with laquer or clear bake enamel to preserve brightness.
    DOW #23
    (Stannate Immersion) MAGNESIUM NONE Under 0.0001
    Gray Layer of tin that retards galvanic corrosion from dissimilar metals. Good paint base and has low electrical resistance.

    DOW # 17 is the proper sealing process for Magnesium Castings. You need to find a processor (See 2nd www.xxx link I have at top of page.) You can paint over it after you are done.

    On the other hand--You can also do the following:

    Clean the inside of the mag rims with a walnut or plastic media based bead blasting process. Do not use metallic media, silicon based material as they could contaminate the Mag. Glass beads should also be okay.

    Spray the inside of the wheels with a light caoting of a good proper zinc chromate primer. A light dusting is good.

    Spray the inside of the rims with a good two part poly-urethane clear coat topcoat paint. PPG or the like. One light coat, followed by two wet coats should do the job.

    This should seal the Mag from most air leaks.
     
  22. teak360

    teak360 F1 Veteran
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  23. dave80gtsi

    dave80gtsi Formula 3
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    Thanks for the info posted here so far, guys - I can always rely on lots of interesting replies when I post on this site.

    While all of the various ideas so far are all good, for my particular circumstances I think they all may be a bit over the top. Remember that I only have a leaky 14" spare tire rim. Seem very clear to me that it has a pinhole leak, and not a crack. Since it is my spare, the only need that I have is that it hold air for a period of time so that it'll be ready to use should I run over a nail with one of my 16" tires. Thus, in a perfect world, I would never need to even take it from the front boot (except to check on the battery, eh?).

    While I have ---NOT--- yet done this, I still think that a can of Fix-A-Flat shot into the tire will serve my needs. I have removed a number of tires over the years which have been "Fixed" in this manner, and what one sees is a gooey mess over the entire inside surface area of the tire and rim. Looks to me that this would be just the ticket for sealing the pin hole.

    Keep in mind that I will never put any miles on this spare (other than to get me home in the event of a nail), so the odds that I will need to swap tires on this spare rim due to excessive tire wear is non-existant. More than likely, I will instead need to change tires in 15 years time due to rubber dry rot, so having a pot full o' goop inside the tire during this time era seems like a reasonable trade-off to me.

    In short, I think that, again for MY specific circumstances, a can of F-A-F will do the trick.

    Does anyone feel -strongly- otherwise? And, if so, why?

    Thanks again to all and Cheers - DM
     
  24. Verell

    Verell F1 Veteran
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    Go for it. It'll either work, or else you'll just have to clean up the F-A-F before you can try another repair. BTW, you'll have to drive a few miles to distribut the the F-A-F around inside the tire/wheel. Also, it'll probably settle in the low spot once the tire is stored, so when you go to use it the wheel will be out of balance. Still could limp home with it that way.
     
  25. don_xvi

    don_xvi F1 Rookie

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    I'll confess that I've never seen inside of a tire/wheel combo that's been Fix-a-Flat'ed, but I wouldn't have thought the stuff would cover the inside of the rim. If you just squirted it in and never drove on it, I'd expect you'd have a pool in one spot on the tire, and if you drove on it the stuff would distribute itself around the outer tread of the tire, but what's ever going to make it go to towards the inside of the rotation?
     

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