Skinpass

Skinpass, also known as skin pass rolling, is a light cold-rolling operation applied to metal sheet, most commonly steel, to improve surface finish and dimensional tolerances after initial rolling. The process uses a cold rolling mill to apply a small thickness reduction, typically only a fraction of a percent up to about a couple of percent, with the aim of enhancing surface quality rather than changing the bulk properties.

The main purpose of a skinpass is to remove minor surface defects, reduce roughness, and improve flatness and planarity. It also helps to achieve uniform surface characteristics for subsequent coating, painting, galvanizing, or forming operations. Because the reduction is limited and the deformation is shallow, the metallurgical structure remains essentially unchanged, with only slight surface work hardening.

Skinpass is usually performed as the final pass in the cold-rolling sequence before coating or further processing. It is especially important for steel strips intended for automotive body panels, appliances, packaging, and other applications where surface appearance and coating adhesion are critical. The process is tuned to meet specified surface roughness (Ra) and thickness tolerances, balancing surface quality with dimensional accuracy.

Potential drawbacks include the risk of over- or under-skinpassing, which can lead to unwanted hardening or insufficient surface improvement. Proper control of roll settings, lubrication, and process parameters is essential to achieve the intended surface finish without compromising ductility or dimensional accuracy.