Bronze Magnesium Wheel Paint

[Bubbas]

Wonder if anyone has successfully recreated the slight bronze color that original magnesium wheels came with. I realize magnesium eventually fades to a dusty grey color. Trying to recreate the original color on current reproduction Halibrand style wheels.

[Cobra_ZA]

Hey Bubbas,

Have a read here:

Dow 7 (dichromate) is a traditional chemical conversion coating used primarily on original magnesium Halibrand wheels to provide corrosion protection and a base for paint. It is characterized by its distinctive brassy, gold, or dark brown finish, which results from a chemical reaction that alters the metal's surface without causing significant dimensional changes.
Purpose and Benefits
Historically, Ted Halibrand used Dow 7 on all his magnesium racing wheels, making it the "factory-correct" finish for vintage Indy and sprint car wheels from the 1950s and 60s.

Corrosion Protection: It acts as a passive barrier to slow down the rapid oxidation of magnesium, though it is often considered a temporary or moderate protection that performs best when sealed with paint.
Paint Adhesion: One of its primary industrial uses is as an excellent primer base for topcoats and organic finishes.
No Dimensional Change: Because it is a conversion coating rather than a thick plated layer, it does not significantly alter the wheel's dimensions, which is critical for precision parts.

Application Process
The Dow 7 process is a multi-step immersion treatment that conforms to SAE AMS-M-3171 Type III specifications.

Cleaning: The wheel must be thoroughly degreased in an alkaline cleaner to remove oils and contaminants.
Activation: The wheel is immersed in an activator solution (often containing hydrofluoric acid) at ambient temperature (70°F–90°F) for up to 5 minutes to prepare the surface.
Dichromate Bath: The wheel is then boiled in a solution of sodium dichromate at approximately 200°F for 30 minutes.
Rinse and Dry: Following a thorough rinse in deionized water, the wheel is air-dried. Drying at 160°F–200°F can further harden the coating and deepen the color.

Modern Availability and Alternatives
While authentic Dow 7 is still available, it has become harder to find due to the use of toxic hexavalent chromium.

Authentic Restoration: Specialty finishers like Saporito Finishing and PTI Industries still offer Dow 7 and Dow 17 (anodizing) for magnesium components.
DIY Kits: Specialized suppliers such as Chemical-Supermarket.com sell pre-mixed Dow 7 treatment compounds for those with the appropriate safety equipment and stainless steel vessels.
Aesthetic Replicas: Because the process is expensive and hazardous, many restorers now use "aged magnesium" paints or ceramic coatings to replicate the look of Dow 7 without the chemical risk, though these do not offer the same chemical bond to the substrate.
Safety Warning: The Dow 7 process involves hydrofluoric acid, which is extremely dangerous and requires specialized PPE and an available supply of Calgonate® Calcium Gluconate antidote gel.