What is mill scale in the context of steel fabrication?

Mill scale is indeed a form of iron oxide that forms during the steel manufacturing process. This occurs when steel is hot-rolled or processed at high temperatures, leading to the formation of a layer of iron oxide on the surface of the steel. This bluish-black coating is primarily composed of iron(II, III) oxide, and it can affect the quality of welds if not removed prior to welding.

Understanding mill scale is crucial for welders and fabricators because it can create challenges such as poor adhesion and contamination in welds if it is not adequately cleaned off before the welding process begins. Proper preparation of steel surfaces helps in achieving strong and durable welds, making the awareness of mill scale significantly relevant in the context of steel fabrication.