Answers (1)
It depends on what you are talking about. Iron corrosion is generally not appreciated and great efforts are made to prevent it. But there is a process called Corten which turns rust into a roofing material. It looks terrible because it flows off the roof and stains the house and everything around it.
Iron nails and corrugated siding are protected from corrosion by letting zinc do the corroding. The process is called galvanized. If a leak develops in the zinc coating, any liquid water will create a battery which electroplates zinc onto the iron to plug the leak.
There is another process for aluminum, called anodize. It is the electrical reverse of plating. Oxidized aluminum is called sapphire, and it is very hard transparent material which protects the surface from further corrosion by weather or other effects.
Brass corrosion is a pesky nuisance and it is avoided by choosing an alloy that does not corrode in the intended application.