I've got some old American magnesium (real magnesium) wheels that I need to clean up. They are badly oxidized (a real dark gray color). What do you guys recommend? I thought about lightly bead blasting with plastic media at maybe 2o to 30 psi, then final hand polish the wheel lips. Any suggestions? As always, thanks in advance for your help. Rex #8089
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Re: Magnesium wheels
Magnesium develops a surface oxide very rapidly, and if you want to keep the lip polished, you'll have to do it at least once a month. It gets old real fast.
A few years ago I made some inquiries through aerospace industry contacts, what if any surface treatments will protect magnesium from rapid oxidation, since a lot of magnesium castings are used in aerospace.
Unfortunately the answer was none - at least that I could find. The surface oxide is actually what protects the metal from further corrosion damage, it just doesn't look very pretty, so magnesium is not a good choice for a decorative part, which is why real magnesium wheels are typically only seen on race cars where long life and cosmetics are of secondary importance to light weight.
A few years ago C5 Corvettes had a short lived magnesium wheel option. I'm sure they had some sort of clear coat, but I don't know the process. There's a very specific process for clear coating aluminum and all the materials (phosphoric acid and Alodine) are readily available from automotive paint suppliers, but I was not able to find what an equivalent process would be for magnesium.
Duke -
Re: Magnesium wheels
A long time ago - when "mags" first came out - American was the first I heard about and they were all 5 spoke with the spokes a dark grey color; even when new. All anyone had to do was be able to afford a set of 5 spoke Americans for the clunker - or a 55 chevy if you had real $ (some will argue the F word here) - and nobody would run you because you had a real hotrod!
All I ever knew anyone did to them was wax them (with carnuba of course). Then "turtle wax" hit the market!Comment
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Re: Magnesium wheels
Duke-----
I believe that the C5 optional magnesium wheels were painted rather than clear-coated natural metal.In Appreciation of John HinckleyComment
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Re: Magnesium wheels
The vast majority of American "Mag" street wheels were aluminum. The magnesium type were way more expensive and pretty much for serious racers only.
Some of the aluminum Torque-Thrust wheels had dark grey painted spokes and the rest was natural. The aluminum flange could be kept polished by a dedicated enthusiast with 20-something energy to polish them every couple of months.
On the other hand, a polished magnesium surface will turn to "mouse hair" in less than a month and it takes a HECK of a lot of polishing to get them to shine again.
Trust me, I spent TOO much time helping a buddy polish the Halibrand magnesium wheels on his GT-40, and that's why I did the research to try to figure out if there was some kind of finish we could apply to keep the shine, but it was in vain.
DukeComment
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Re: Magnesium wheels
That could be, but whether a color coat of clear coat I expect there is some kind of prep process one must go through to get good adhesion - similar to what's required to paint or clear coat aluminum, which I've used with excellent success, but I was never able to find a specific "industrial strength" magnesium coating procedure.
DukeComment
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Re: Magnesium wheels
Duke-----
There must be one. Some late C3 valve covers were magnesium and painted. Also, all 1984-92 Corvette small block valve covers were magnesium and painted. The paint adheres very well on these covers, so they must use an effective process.In Appreciation of John HinckleyComment
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Re: Magnesium wheels
------My old drag car had Magnesium front-runners and after awhile I found that Scotchbriting the lip worked far better than polishing. Granted the finish wasnt quite as show-worthy as polishing but the sanded finish lasted far longer and was easier to do when I did need to freshen the wheels up. A win-win deal...........Bill SComment
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Re: Magnesium wheels
Lawn Boy, back when they still made mowers by OMC, had decks that were made of magnesium and painted green. Now lawn boy is owned by TORO and they put Honda engines on them. Go figure.Comment
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Re: Magnesium wheels
Rex -
How old are they? Magnesium doesn't age well (structurally) without special coatings; they may be better suited to display than to spirited driving.Comment
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Re: Magnesium wheels
John,
I am not sure of the age. They appear to be NOS, I purchased from a gentleman in Texas a couple of years ago. They look great except for the dark gray oxidation. I had planned to put them on a midyear for limited street use. I guess now I'll have to use them since I just sold my aluminum versions of the same wheel. Thanks, RexComment
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Magnesium wheel protection
I asked the material scientists at Boeing what the best stuff availble would be for this application and they said the best stuff for protection against oxidation on Magnesium is probably a product made by Zip Chem Products called Cor-Ban 27L (ZipChem ZC-027L). They are located at 400 Jarvis Drive, Morgan Hill, CA 95037
It is a non drying paste type wax, apply it and wipe off the excess, should be good for about 6 months.
There is also a corrosion resistant product called Boeshield T9, however Boeing recently removed it from our approved products since the manufacturer chaged the formula.Comment
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