Hot-rolled pickled and oiled (P&O) coils undergo an additional step after the hot rolling process. Once the coils are formed, they are immersed in an acidic bath, usually containing hydrochloric acid, to remove the surface scale or oxidation. This process is known as pickling

After pickling, the coils are then oiled to prevent rust formation and improve their surface finish. These processes enhance the surface quality and prepare the coils for various applications. The pickled surface is smooth, free from scale, and has a consistent appearance. The removal of scale and impurities allows for better adhesion of coatings, paints, or other surface treatments that may be applied later.