Carburetor Body Finishes

There are three main materials of which carburetors are made: cast
iron, zinc and aluminum. Starting in the 30s, cast iron started to be
replaced by zinc and in the late 50s, aluminum replaced a lot (but not
all) zinc.
In most cases, cast iron is finished in black oxide though
its sometimes painted black. Carter regemended a special black
carburetor paint when rebuilding a carb. Thus, while carbs like the W-1 Carter were originally black oxide finished cast iron, many of them are now - correctly - a semi-gloss black.
Rochester carbs also used cast iron in the throttle body section.
This part was always black oxide and there was no factory paint
regemendation.
The most well-known carburetor material is olive-green colored zinc.
Zinc itself is a bright silvery metal that reacts with air and water to
make a powdery white material often called white rust . To prevent
this, carburetor parts are treated in the factory with a chromic acid
solution, which forms a thin layer of zinc chromate on the surface of
the metal. This very effectively protects the metal underneath from
being damaged by water or air. This is why carburetors are usually
green!
The last finish is natural aluminum, which is found on carbs like the Carter AFB(Aluminum Four Barrel) and Ford 2100/2150.Here are some of the finishes found on various types of OEM carburetors:Holley 2300, 4150, 4160, 4180 (modular carbs): main body, float bowls and other cast parts are green chromated zinc; throttle bodies are aluminumHolley 2140, 4000 (Tea Pot): main body is natural aluminum, upper parts are green chromated zincHolley 2100, Ford AA-1 (flathead carbs): throttle body is black cast iron, float bowl and air horn are green chromated zincRochester Quadrajet: float bowl and air horn are chromated zinc; throttle body is natural aluminum; choke housing is aluminum except for early Oldsmobile 4MC carburetors and early Pontiac M4MC carburetors; marine throttle bodies have a special blue/gray conversion coatingRochester 4-Jet (4G, 4GC), 2-Jet (2G, 2GC, 2GV) and Model B (B, BC, BV): most throttle bodies are cast iron (black oxide) but a few are aluminum (see Rochester 4G guide ); float bowl, air horn and choke housing are green chromated zincCarter WCFB: most throttle bodies are cast iron (black oxide) but a few are aluminum (very rare!); float bowl is green chromated zinc; air horn is natural aluminum; choke housings are usually zinc, but sometimes aluminum in later modelsCarter AFB: aluminum, all the way... except for the choke housings, which were usually green zinc in 60's carbs. One version of the 'Aluminum Four Barrel' was cast of chromated zinc and used on Ford marine engines. This is quite rare.Stromberg: most classic Stromberg carburetors, such as the EE series (including the '97' used on Ford flatheads), AA series (found in many applications, notably Buick gepound carburetion set-ups) and BX one barrels (used on various makes, especially Dodge flathead 6 cylinders) used a cast iron (black oxide) throttle body, with the rest of the carb in green zinc.