4.Mechanical plating - This coating is done for small steel parts and products, usually around 8-9 inches and weighing less than half a kg. The automatic plating process cold welds the steel particles to a workpiece for applying a coating. It is done by putting small parts in a barrel with zinc. The steel parts are cleaned and flash copper coated before going into the plating barrel. The barrel contains zinc powder, glass beads and other proprietary chemicals. The next step in this process is tumbling the barrel, wherein the glass beads peen the zinc powder onto the product. At last, the coated products are treated with a passivation film, dried and packed.
5.Inline galvanising – In this galvanisation method, steel tubes are tumbled in a pool of molten zinc, after which a conversion coating is applied to the steel tubes to avert the formation of zinc oxide and hydroxide. The conversion coating is also topped with a clear and inorganic topcoat. It is noteworthy that only the outside of the tubes undergo this process; the inside surface only gets a coating of zinc-rich paint. This method is used when coating thickness and ductility control is needed.
6.Sheet galvanising – Sheet galvanising is another hot-dip process applied to products like steel sheets, strips and wires. This process begins with cleaning the base product in an alkaline liquid, brushing, rinsing and drying. The steel then passes into the heating or annealing furnace to impart the desired strength and formability. In this furnace, the steel is put under a reducing gas atmosphere to eliminate any oxide from the surface. The steel enters a vacuum chamber to prevent air from reoxidising the heated steel product. The steel then gets into the molten zinc bath before being sent around a submerged roll to create the bonded coating. The product finally gets withdrawn from the tub, and an air knife is used to eliminate any excess zinc.
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