Without protection many metals will corrode quickly. There’s a big range
available, so Faye described how they work.
Etch Primer makes a strong bond between metal and your paint, preventing it from
peeling off. It works by etching into the metal surface to provide a key for the
first coat of paint to grip.
If you were to install an unprotected steel gutter, it might only last one year
before rust holes develop. Galvanised guttering has been treated in the factory
with zinc, which provides a sacrificial coating that corrodes before the steel
does. This helps it last 50 to 60 years.
You can get this same zinc protection by using Cold Gal. It can be applied with
a brush or spray can, and can be used to restore protection on damaged
galvanised steel (say where it’s been cut, welded, soldered or drilled) as well
as raw steel. Raw steel to galvanised steel in an instant!
White Knight products are available at all good hardware stores.