I had the rims on my COE powder coated. They were are also 20" rims. It cost me $50 per wheel to have them blasted and coated in silver and then again in clear, which I thought was fair. The only problem I see is if I ever need to touch them up, I will have a very hard time doing it. On the up side, when the tires were mounted they barely scratched the coating, its very tough stuff.
Scott

1947, 1950, & 1952 Chevrolet 1/2 ton
1952 GMC 450 series Cab Over Engine
1946 Chevrolet 2 Ton