Painting Magnesium

[keefer]

does anyone out there know of anyone who can spray some Mag wheels.
I have just been on to Dymag and they want £170.
I only want them done in gloss black and cant see why it should be so expensive :o

[Old Yella]

Think its not just a case of spraying em, think they need a special primer/sealeant.

To get em blaste dclean and powder coated is the best part of £80 inc vat so its only double, sounds a lot but Mags need looking after or you might end up with an expensive pair of ornaments.

Jasp had some done not so long ago if you want to speak to him.

[Old Yella]

Try this link.
http://217.199.188.40/xmb/viewthread.php?tid=3987#pid31155

Copy and paste to your browser, good info

[keefer]

the thing is they will be brand new any way so I don't think they will require much prep. Maybe just a light sand.
And as you said I know powder coat will only be about £60-£70. But can Magnesium withstand the heat of powder coat ?
Cant believe Dymag they make them but want to rip you off to paint them
:flame:

[Old Yella]

Mentioned in the post about whetner they can stand up to the heat of powder coating?

[Shazaam!]

I was initially concerned about running mag wheels on the street because once the coating gets chipped by a stone you've lost protection. I am very impressed with the coating on the Dymags I bought. My opinion is that it's worth the extra money.

Like Old Yella says, it's all about surface preparation. Be mindfull that untreated magnesium corrodes quickly when exposed to moisture in the air. The proper way is to strip them with a special solution etching cleaner, then a special conversion coating, then an application of self-etching primer, then your color choice. Finally, a two part clear coat finish is desireable for added toughness.

Here's an article on powdercoating that may help you to decide.

http://my.execpc.com/~davewrit/Powder.html



[Edited on 11-30-2004 by Shazaam!]

[keefer]

thanks for that shazaam. what I really want to know is whether you can coat over the coat that is already there ?
as it will be brand new anyway.
I am not happy with the Dymag price as they were coating Machesini wheels last year for around £120
so to be quoted £179-200 is outrages especially when I only want the spokes done as they are carbon rim items. anyway its the usual you have a Ducati so you must be able to pay more than everyone else

[Shazaam!]

I'm wondering if the reason for the higher price isn't a charge for removing the carbon rims prior to stripping, painting and oven curing. I'm not sure it's OK to send carbon fibre through the oven after powdercoating either.

[keefer]

no no, wouldn't do that we are just talking about the centres here

[yeti]

Am no expert on magnesium, however using a bit of common sense here:-

The wheels are new, therefore the protection should already be in place and undamaged. So no need to worry about that. Furthermore, I think I'm right in thinking this is purely a cosmetic paint job.

Suggest you can carefully flat the original painted surface taking care not to go through it, then paint over the top with any paint that doesn't react to whats already there.

Shame you are so far away, we could have done it for you for not a lot. It's not a big deal.

[skidlids]

Yep I suggest flatting back and a good can of smoothrite

[yeti]

Not sure I would use smoothright, artex is far more durable.......

[skidlids]

Snowsem

[yeti]

Snowcem - [smug]

[skidlids]

At least you knew what I meant

[yeti]

:sing::pig::sing::sing::sing::sing:

[yeti]

Or tar, that would be good as the wheels are gonna get covered in it anyway or UNDERSEAL

[keefer]

Originally posted by Shazaam!
I was initially concerned about running mag wheels on the street because once the coating gets chipped by a stone you've lost protection.

don't get this as there are parts on the wheel that are not protected anyway like the face that mounts up with the hub and the centre nut on the rear wheel ?

[Shazaam!]

Unlike aluminum, bare untreated magnesium deteriorates quickly when exposed to moisture in the air, so Marchesini, Dymag and Mavic put a dichromate coating on the surface to avoid corrosion prior to final painting. This Dow #7 coating offers only fair corrosion protection (less than 24 hours 20% salt spray resistance) according to the Mil Spec [MIL-M-3171C]

Impacts from small stones and other debris will damage this coating and expose it to the weather, so an expensive magnesium wheel or swingarm should be painted or powercoated prior to track or street use. Some mags like Dymags come powdercoated with a tough clearcoat direct from the factory.

If corrosion has already started, you need to use a chromate pre-treatment compound like Alodine 1200 that prepares the surface of the magnesium. Then you can paint it like any other metal.


Dow Magnesium Processes [MIL-M-3171C]

Dow#1: A chrome pickle treatment for magnesium. Color varies from matte gray to yellow-red. Only fair corrosion resistance (less than 24 hours 20% salt spray resistance). Removes metal (Approximately .0006" for wrought material, less for castings). No dimensional change. Used mainly for protecting magnesium during shipment, storage, and machining. Can be used as a paint base.

Dow #7: A dichromate treatment for magnesium. Color varies from light brown to dark brown to gray depending on alloy. Only fair corrosion resistance (less than 24 hours 20% salt spray resistance).

Dow #9: A galvanic anodize treatment for magnesium. Produces a dark brown to black coating. Designed to give a protective film on alloys which do not react to Dow No. 7 treatment. Only fair corrosion resistance (less than 24 hours 20% salt spray resistance).

[keefer]

so is that bit of wheel I mentioned actually protected ?

[Shazaam!]

Yes, as long as the coating remains undisturbed.

[Edited on 12-1-2004 by Shazaam!]