Rustoluem 2X spray or canned enamel paint.
Here are some ideas I found for you..
Arthur, have you considered using a spray paint? They make them specifically for out door furniture that is metal or plastic or wood. It will say on the can. Be sure it says it can be used for any out door type decor.
I spray paint my metal patio set ever 4 or 5 years. We live on a lake and it gets a lot of use. I use black metallic paint, spray it in my front yard (out of the wind) and I'm good to go!