Corrosion of steel from new to painting. When steelwork is produced from molten iron and passes through the mill to form shape when cooled it is light blue in colour and known as Mill Scale.
This finish is where the layer of of molten steel is deposited back onto the fabricated body of produced steel items such as stanchions and girders. This layer of the molten steel needs to be removed before painting. This can be done byway of natural weathering, grit/sand blasting, flame cleaning or acid cleaning.
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| Mill Scale | Weathering commenced | Flaking of the mill scale | Rust removed by any of the above methods including wire brushing |
During natural weathering the layer of mill scale becomes detached and once removed the surface will be left with very fine particles of steel referred to as Rust.