Flat products which must provide corrosion resistance are coated after annealing. Typical hot-dip coated products include galvanized strips for automobiles, building materials and home electrical appliances, and tin- and chrome-plated strips for food and beverage cans and other containers. For reasons of efficiency, coating of continuous strip is more common than coating of cut sheets. Coating processes are broadly divided into hot dipping and electroplating. The hot dip process is more suitable for heavy coating weights, and electroplating for lighter coatings. Electroplating is often used to apply a thin coat of expensive tin, and hot dip is used for heavy coatings of inexpensive zinc. The figure shows an example of a hot dip galvanizing line. After passing through the pretreatment tanks for degreasing, pickling, and cleansing, the strip passes through the annealing furnace and a pot containing molten zinc. The annealing furnace is used to apply the heat cycle needed to obtain the required mechanical properties and activate the surface with a reducing gas, which makes it easy to coat zinc on the strip surface. The coating weight is controlled by a purge gas jet blown on both surfaces of the strip from a nozzle above the pot, to remove excessive molten zinc. The cross section of a galvanized strip is composed of the steel substrate, iron-zinc alloy layers, and a zinc layer. Because the paint adhesion and weldability of the surface of this zinc layer are not necessarily good, galvannealing has been developed to improve these properties. In the basic process for galvannealed strip, the zinc-coated strip emerges from the pot and is heated in a galvannealing furnace, forming an iron-zinc alloy layer by the interdiffusion of iron and zinc coating layer, so that the surface of the zinc layer also contains some amount of iron. The galvannealing line is usually equipped with a skinpass mill, a tension leveler, and chemical treatment equipment for chromating, following the galvannealing furnace. For automotive steel strips, a thin iron plating is sometimes applied electrolytically to the iron-containing zinc layer to improve the sliding property between the die and material during press forming and adhesion of paints in electrostatic coating. In this case, electrolytic plating equipment is installed in the line. Typical products from a hot dipping line are galvanized sheets and zinc-aluminum plated sheets for building materials, galvanized sheets and galvannealed sheets for automobiles. Special products are aluminum coated sheets for car mufflers and lead-tin alloy-coated sheets (terne plates) for fuel tanks.