The acid pickling line is a key piece of equipment for metal surface pretreatment. It mainly targets coils (or plates) such as cold-rolled steel coils and hot-rolled steel coils. Through the chemical action of acidic solutions (such as hydrochloric acid and sulfuric acid), it removes surface oxide scale, rust and residual impurities, providing a clean and activated metal matrix for subsequent processes such as hot-dip galvanizing and coating.