POR15 makes a clear coat catalyzed urethane that is terrific, VERY
strong, especially in humid (body contact) environments. Not cheap
but it is good for 15 years sun exposure. negative, it is very tough
to take off if needed. Incralac is a copper specific clear coat,
good UV protection and can be removed with MEK is needed. Not nearly
as tough as the POR product above, but offers protection, easy
removal if needed.
Also, the POR product is a much thicker coating than the Incralac.
The mfgr of Incralac also makes a water based product but I not
little of it as I never use it. Incralac was originally developed to
be used for bronze sculpture that was outside.
Also clear powder coating might be something to look at but sharp
edges do not take good coverage, but this is true of most any
Hope this helps.