Yes. Mild steel, also known as carbon steel, will rust over time unless it is treated with some sort of protective coating to prevent the steel from coroding. Mild steel has a low carbon content, and the carbon does not help prevent the steel from rusting.

How quickly does steel rust?

Steel is a metal that holds a lot of iron, and let's say, for instance, that steel is constantly surrounded by environmental factors like water and oxygen, the steel may start to see signs of rust in as little as 4-5 days. At the same time, there are different types of steel that can rust slower or faster than others.

Why does steel rust easily?

Iron, as well as iron alloys, rusts because of a chemical reaction known as oxidation. When iron is exposed to moisture or oxygen, oxidation occurs. During this chemical reaction, iron is converted into iron oxide. The iron oxide typically has a reddish, flaky appearance that becomes progressively worse over time.