As metals such as iron or steel are affected by the elements they begin to corrode and produce a layer of reddish-brown oxide called rust.
This can be prevented by painting, galvanising or lacquering these metals; however, where there are cracks the surface will quickly begin to corrode and show rust. Though it weakens the metal, it’s a very attractive finish with which perfectly clean metals are painted and finished to look as though they have rusted. A clear sealant will hold the colour to the metal.
Solid metal bars can also be deliberately rusted outside, rubbed down lightly and then sealed
Cor -Ten steel in sheets is a very attractive rusted metal that can be used for furniture and construction with impunity.