An Etch primer would actually eat into the metal and give a superb level of protection

You would have to take the waxoil off yes, but if u painted over the etch it would last years n years before rusting. (aslong as you've sanded it all down to good bare metal)

When our company made it for the UK market (still does but for the US) it comes with a 10 year anti-rust warrenty. When used properly it really is that good!