Sealing Porous Magnesium Alloy Wheels?

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.

 

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.

 

How about radial tire inner tubes, such as ones available from Coker Tire?

 

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
[email protected]
www.rogerkrausracing.com

 

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.

 

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

 

Who gave you this advice?

 

Ditto That.

 

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.

 

There sure are some odd tire theories floating around the Netherlands!

 

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.

 

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.

 

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.

 

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.

 

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.

 

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.

 

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.

 

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

 

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.

 

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.

 

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.

 

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?