How to Polish Raw Magnesium and Aluminum

[oldGSfan]

Greg (where did I get Rick from?) - as you can see the finish is corroded off in spots already, and has likely been that way for many years. I am not sure if the reason to not leave it bare is due to cosmetics, or the magnesium's structural integrity is the issue. Since it turns black and some like to polish old real 'mags' I hope it's the cosmetic aspect that is the reason, and since they will be painted not polished, maybe it's OK?

I have read to absolutely do not use chromate, use self etching primer. Others say use zinc chromate. Witchcraft I tells ya!

Don't leave the rims without a coating for more than a couple of hours.

[GregT]

Greg (where did I get Rick from?) - as you can see the finish is corroded off in spots already, and has likely been that way for many years. I am not sure if the reason to not leave it bare is due to cosmetics, or the magnesium's structural integrity is the issue. Since it turns black and some like to polish old real 'mags' I hope it's the cosmetic aspect that is the reason, and since they will be painted not polished, maybe it's OK?

I have read to absolutely do not use chromate, use self etching primer. Others say use zinc chromate. Witchcraft I tells ya!

It's mainly the mag's structural integrity. Unfortunately my best reference book is out on long term loan but aircraft practise is the best policy to follow. Car mags are not stressed as close to their material linits as bike rims - at least not nowadays. I do remember well a set of early Brabham mags breaking up in street use. Bike rims of the period you have are noted for their propensity to crack. These cracks start from surface blemishes like corroded spots. Which is why I strongly suggest media blasting followed by crack testing.
If they're cracked then any discussion about finish is moot. They become ornaments.

And i strongly suspect I'm the polar opposite of Rick. In any way you choose.

[oldGSfan]

OK thanks for the info. I will get them blasted clean, then primed soon after. I have a neighbor that runs a powder coating shop so they should be able to bead blast them for a nice price. I'd hate to invest then find out they are junk, so I"m lucky to have that resource. Then I'll have them tested, I'm sure there are places near me in SoCal.

I have a brand new set of stock wheels taken off in '82 and stored, but these will be much more interesting. They are 18". 3.5 rear and 2.5 front, and rubber is scarce. Shinko seems to be the only choice in the size I want.

I removed the bearings in the front, rear is more, umm, interesting. One side came out fairly easily, but the chain side has two bearings back to back, and I suspect a circlip between them. There isn't much purchase to be had. I'll get there, fngers crossed.

I'll lay off the corn squeezins when posting and get names right in the future... hopefully.

It's mainly the mag's structural integrity. Unfortunately my best reference book is out on long term loan but aircraft practise is the best policy to follow. Car mags are not stressed as close to their material linits as bike rims - at least not nowadays. I do remember well a set of early Brabham mags breaking up in street use. Bike rims of the period you have are noted for their propensity to crack. These cracks start from surface blemishes like corroded spots. Which is why I strongly suggest media blasting followed by crack testing.
If they're cracked then any discussion about finish is moot. They become ornaments.

And i strongly suspect I'm the polar opposite of Rick. In any way you choose.

[GregT]

I like the term "corn squeezin's" LOL. probably good paint remover.

If you have to, the outer bearing can have a piece of strip steel welded across it to give you something to bang on.