The problem Ted is the surface finish on those clamps. No matter what coating you apply the rough finish means that unless the coating is unusually thick the rough spots will break the surface of the coating, that allows water access and that means rust, in a relatively short time they’ll look as bad as they were before you started.
I’m experimenting with grinding the rough surface off and then either chroming or ceramic coating them in a chrome like finish. However, it’s time consuming and boring to prep the clamps.
However that’s almost free to do and the ceramic finish isn’t very expensive, about £5-10 per clamp.
Delkevic is far cheaper but it’s nowhere near as attractive as the 4 into 4 system, you pays yer money and takes yer choice.