Steel roof sheet or Metal sheet is popular these days, they last long for over 10 years, and each sheet will be coated with aluminum and zinc alloy to prevent the rust.
But…it would be worst if the steel roof sheet gets rust too soon, this article will share what are the things that can damage the coating for your reference.
One of the materials that will damage the coating is metal scrap from cutting the sheet with a grinding and cutting disc. When the metal scrap comes in contact with the aluminum-zinc-coated steel roof, the service life of the sheet is shorter. Some cases, remain only 1-2 years after that gets rust.

After the installation, the roof installer will clean up the roof sheets and make sure there is no materials or scraps left on the roof. Anyway, rust also can occur from the scrap materials which come from other houses’ roofs and fall on our roofs.

There are also other materials that should not contact with the coated steel roof otherwise, it will rust too quickly, for example lead, copper, wet and dry concrete, soil or stainless etc.