Ok, admitted newbie here, so I have to ask: I've seen, I'd guess 60's era mag wheels in a bronze finish. These were wheels with with holes verses spoke style. Was this finish due to the metal used or was it a special paint? Was it a certain manufacture who produced them during a certain window of time? Hope that all doesn't sound to vague.....
That's called a DOW 7 finish. It is an anodizing treatment done to items made from magnesium to keep them from corroding. Google "magnesium wheels dow finish" for many photos of race wheels in this finish.
Thanks for the info! Did a search as you recommended and found lots of info out there! As that guy on the radio used to say...."and you know the rest of the story"
If the 60s era wheels you are asking about were aluminum, they were NOT Dow 7 coated, and they were NOT gold colored either. They were natural aluminum color that only appears to have a gold hue in certain light conditions or in some photos. A good example are the American "Daisy" 5 spoke aluminum wheels. You can find multiple posts all over looking for the source of the "gold" color on these wheels when in reality they were never gold at all.
I bought a set of four gold colored real magnesium bolt on 15 inch wheels in the late 60's. Problem was, NHRA wouldn't allow real mag wheels on stock class cars, so I painted the center part black and polished the outer edge. Works for me.
From what I have read, Halibrand is the only company who offered the Dow7 finish on their magnesium wheels.
The Dow 7 was only to keep the magnesium from tarnishing on the shelf. That's it and it wore off very quickly with use and exposure. Quick like 2 weeks.
Strange, because I bought a new set of Halibrand midget (12") wheels for the front of the dragster in my avatar in '62, and they kept their bronze finish for the year or so that I ran it (never knew it was Dow7, though, until this post.
Type III (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).Precleaning and pickling may result in dimensional changes due to metal loss.
the finish on mine lasted over 35 years, but they were on a drag only car & never cleaned with more than reg soap & water. You can see there was no color change between the outside & inside
I don't know how long the treatment last but on our sprint car back in the early 70's the gold to bronze color hung around a while.
Glad this post has been helpful for some! Does anyone know what year this coating was first used by Halibrand? All I've found so far is "used in the 60's" Posted using the Full Custom H.A.M.B. App!
We use Dow 7 solution at work on magnesium aircraft parts. Yes, it turns magnesium to a color that varies between brown and light gold depending on how hot it is mixed. Generally it is just a pre-coating to 'pickle' the bare magnesium before coating it with epoxy, but on areas that are left exposed, like mating surfaces, the yellow tint lasts a long time in the elements, again varying on how hot it was mixed. Posted using my Lil' Orphan Annie Secret Society Decoder Pin
Oh, and yes you can still buy it. BUT it is some really nasty stuff and contains lots of bad stuff like chromic acid, so unless you have deep pockets and a good set of protective gear, I'd forget about it... Posted using my Lil' Orphan Annie Secret Society Decoder Pin
As stated it is a chromate conversion coating. Applied by chemical dip. The active ingredient is hexavelent chromium, which is carcinogenic and also an environmental hassle. BTW, hex cromium is also called yellow or gold chromate. The same thing that makes the fasteners or hardware that used to be called "gold cad" as in cadmium plating. Now it is zinc instead of cadmium, but zinc can also be treated with the yellow or gold chromate.
The first Halibrands were used around 1950. First were "smoothies" then came the slots. I think it's safe to assume they were coating the wheels at that time. It's hard to find color photos of the wheels with the Dow 7 coating still on. A lot of the cars had painted or polished wheels. 1952
Not sure the Dow 7 coating will work or come out the same on aluminum. They do make a powder coating that I saw recently to put a similar finish on aluminum wheels, and it runs about $75 a wheel I think.
I think you -could- use Dow 7 on Aluminum, but I'm not sure how it would turn out. The stuff we get at work is labeled specifically for magnesium. I would assume that any aluminum wheels that are gold colored are treated with Alodine rather than Dow 7. Alodine is a Cadmium-Anodizing solution specifically for aluminum. Much easier to come by and use than Dow 7, and accomplishes the same goal. Posted using my Lil' Orphan Annie Secret Society Decoder Pin
may want to check MSDS before considering any of these treatments. Alondine...http://hybris.cms.henkel.com/henkel/msdspdf?country=US&language=EN&matnr=594418
Alodine is the chemical conversion for aluminum. It makes it more yellow than gold. It is a common surface prep prior to painting.
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