Powder coating issues with the Mags

I had my Chromodoro mags powder coated about 15 years ago with good results. The key is to pre-bake the bare mags for a few hours to drive all the moisture out.

That said, many knowledgeable guys don't recommend powder coating for mags because small cracks would be undetectable.

They sure are easy to clean now -brake dust just hoses off.

 

Like Mike said, they must be outgassed prior to coating and they might even have to be coated hot, usually outgassing is enough. Outgassing is heating the wheels to cure temp for a 1/2 hour and it must be done to some metals and even old metals that normally do not need it. That is not putting them in a oven for a 1/2 hour, that is a 1/2 hour after the wheels are at cure temp, usually 450F. The only concern I would have is that since they have been heated twice already, the outgassing should be have been done already unless they re-introduced something when removing the first coat, such as paint removers.

I have had (very rarely) to coat things when they were hot, outgass them at cure temp and then with the part as it is cooling at around 200 F. coat, that should solve all the gassing problems but its tougher to get a good coat because the powder immediately starts to melt and flow. Powder Coating hot parts is pretty hard to get a uniform coat but sometimes must be done. Usually you only coat a part hot for a second coat, such as a clear coat.

And, no I don't do this for a living, but I have been Powder Coating for about 5 years as part of my restoration hobby. I love Powder, its so much better than paint. I hardly ever paint anything anymore.

In the Powder Coating world, there is a group that believes you should not powder wheels and suspension parts since it can hide cracks and another group that says its perfectly safe, like everything you have to look at all the evidence and decide for yourself. Me ? I painted my Dino wheels but only because I did not have a oven big enough to cure the wheels at the time, now that I have a big oven, I have considered re-doing the wheels. And I did Powder the wire wheels on my 1934 Singer along with all the suspension parts on that car (now you know which group I belong to)

 

I can appreciate the safety factor, but all things aside, how often do the wheels, and paticularlllly the suspension get inspected? For a Race car, probably a lot closer than the average street machine I would sure think, But in reality, I would have to be honest. I couldn't describe my daily drivers wheels if I had to (OEM steel, whoopie).
My point being, I would sure be curious if there were any stats, reports, etc. to give us a realistic picture of the "danger". I would tend to think that if looked at closely, the real reason is liability.
Not being a pest mind you, but I can't recall the last time I had heard of a street wheel breaking on a public road.

 

Remember, when the wheels fly apart at speed, Ferrari's self distruct, split in two, and kill the occupants.

 

I have never powdercoated Ferrari mags, but I have had serious issues with continued outgassing when doing some other mags, even when properly done.

That's why some shops won't touch them...

Bill

 

I think he is just saying "be careful as wheel failure at Ferrari speeds can result in a an accident of light aircraft proportions". You dont see many wheel failures on road cars because most road car wheels arn't made out of Magnesium which isn't really suitable for road wheels.

Servicing a car with mag wheels should include close inspection of them as Magnesium tends to crack rather than bend (more brittle than aluminium, which is brittle anyway).

I work with a company who runs a fleet of 355's and they have just replaced 6 sets of wheels, from the 24 old wheels they removed you could make one set in need of refurb all the others are only fit for meltdown or a coffee table.

 

They had done over 40,000m, with 20,000m+ on track (although not being driven flat out), I imagine the damage was done from clipping apex and exit curbs. Although the curbs are rather low and gentle they do rumble over them at speed. With magnesium wheels (that are painted) the first thing you notice is drops in tyre pressure (like a slow puncture) because the cracks let the air out. I'm not sure if powder coating lets the air out, hence my recommendation that powdered wheels are inspected regularly.