Gunmetal is our standard finish, and is mild steel, dark anthracite in colour. Before it leaves our factory, we oil treat it to protect it. Treat it like a wok, and if any surface rusts appears, rub it down and apply any vegetable oil to protect once or twice a year. If kept under cover, should be trouble free.
CorTen is our pre-rusted finish, made of a special copper impregnated steel that rusts as a protective layer, not corrosion – this is an expensive material, hence the price differential. It will last several decades untreated, and is the same material as the Angle of the North. Perfect for that instant rustic or industrial look. Needs almost no treatment, and can be left outside without covers.