Pickling, prepares the surface for subsequent processes. This process, separates the oxides from the surface by immersion in an acid tank. Then the acid is rinsed and the steel is dried. Ultimately, the surface is greased to protect against oxidation. As pickling continues in production line the temperature of acid increases, as a result it is necessary to keep the temperature of acid tank in a desired range by a heat exchanger; So that excessive temperature increase, does not cause harm to the product.