Galvanizing process

Galvanizing process

Galvanized method refers to the surface of metal, alloy or other materials coated with a layer of zinc to play a beautiful, rust, oxidation resistance and other surface treatment technology. Now the main method is hot dip galvanizing. The effect is twofold: to act as a barrier against environmental corrosion and to preferentially replace corrosion at the point of layer rupture.

Galvanized steel and cast iron has a long history, its output is increasing gradually, and its use is becoming more and more extensive. This is because the price of zinc is relatively cheap, easy dipping and plating, after beautiful appearance, and in the corrosion environment its surface can form a layer of excellent and corrosion resistant surface film, zinc can play a cathodic protection effect on iron in electrochemical corrosion, this is because zinc has more negative electrode potential than iron, when zinc and iron constitute a microbattery, zinc is the anode, iron is the cathode, in the corrosion, Zinc dissolves and iron is not damaged, so zinc acts as a cathodic protection on iron [1] to the sacrificial anode. Taking advantage of these properties, zinc materials have been widely used in building materials, pipes, household appliances and so on. In recent years, with the improvement of zinc method, the decrease of cost, the improvement of quality, the diversification of varieties, so the use of more and more wide, increasing quantity.

The Silas method

Also known as direct flame heating method; First, the strip is degreased by alkali washing, then the surface of the oxide skin is cleared with hydrochloric acid, and after washing and drying, it enters the vertical inline annealing furnace directly heated by the gas flame. Through strict control of the flame ratio of gas and air in the furnace, the incomplete flame firing is carried out under the condition of excess gas and insufficient oxygen, so as to create a reducing atmosphere in the furnace. The strip is heated to recrystallization temperature quickly and cooled in low hydrogen protective atmosphere. Finally, the strip is immersed in zinc solution under closed condition for hot-dip galvanizing. This method has the advantages of compact equipment, low investment cost and high yield. Sharon Process: In 1939, the American Sharon Company put into production a new hot-dip galvanizing unit, so it was also called Sharon process. The process is to spray hydrogen chloride gas into the annealing furnace and make the strip steel reach the recrystallization temperature, so it is also called gas pickling process. The use of hydrogen chloride gas pickling can not only remove the oxide skin on the strip surface, but also remove the grease on the strip surface. Because the strip surface is corroded by the oxide gas, the coating obtained by the Sharon process has a particularly good adhesion. However, due to the serious corrosion of the equipment, it causes high equipment maintenance and replacement costs. So this method is rarely used. Improved Senjimmy: It is a more superior hot-dip galvanizing process; It connects the independent oxidation furnace and reduction furnace in the Senkimire process by a small cross-sectional aisle, so that the whole annealing furnace, including preheating furnace, reduction furnace and cooling section, constitutes an organic whole. The practice has proved that this method has many advantages, such as high quality, high yield, low consumption and safety.