I too have had good results with the Eastwood SG chassis black. If there is some rust on the frame, a first coat of Eastwood black rust encapsulator primer would help it last longer.

If you want to keep cost way down and have access to a small sprayer, hit it with SG black Rustoleum from the hardware store thinned with 10-15% paint thinner... or just brush it on. SG black is very forgiving.