Typical Steps in the manufacturing process of Galvanizing

1) Cleaning: The step in which the majority of oil, grease, and paints, are removed with a hot alkaline cleaner.

This cleaner usually consists of a lead bath or hot soapy water.

2) Rinse/Air Flow: A bath of cooled water to rinse any of the cleaning residue off and air knives to aid in the removing of any additional residue and water that were used on the material before entering the pickling system .

3) Pickling: A bath of diluted hydrochloric or sulfuric acid solutions that serve to remove surface rust and mill scale to provide a chemically clean metallic surface.

4) Rinse/Air Flow: Another water reservoir to dilute the acid concentration that may be left on the material before entering the flux stage and also an air knife to aid in removing un wanted residue.

5) Pre fluxing: The steel is immersed into a liquid flux to remove oxides and to prevent oxidation prior to entering the molten metal. The liquid flux is a concentration that consists usually of zinc ammonium chloride solution. The flux is the key ingredient in aiding in the ability of the zinc to adhere to the iron or steel.

6) Air Flow: Between the pre flux area and the molten metal the material is blown dry using a air knife to remove in moisture that consists prior to entering the liquid metal.

7) Galvanizing: The item is immersed in a bath of molten zinc, with a temperature range between 820 and 850 degrees Fahrenheit. The temperature needs to be constantly in this range, if too cold, the zinc  freezes,  if too hot, the coating consistency is not symmetrical causing low coating, bare spots, or a burnt gray color to exist on galvanize. the material. With the temperature within range the zinc metallurgic ally bonds to the steel, creating a highly resistant zinc iron alloy layer. The zinc iron alloy is formed in the galvanizing process with pure zinc and the ferrous material being galvanized. This alloy layered is a bond between the iron that is diffused from the steel product being galvanized and the zinc in the molten stage. The layer of coating has several different phases of alloy layers with names such as Alpha, Gamma, Delta, Zeta, and the free Zinc layer. Each of these layers have a different amounts of iron, zinc ratio's. This alloy layer is dependent on the type of steel being used for the galvanizing process. These different alloy layers are what make up the weight of coating that the material receives, determining the finished gauge of the product. The layer gauge to be put on the material is determined by the time in which the material is actually in the zinc bath.

8) Finishing & Cooling: These two steps work together because the cooling of the material results in the finishing of the material. The finishing process consists of removing excess zinc by draining (to aid in the drainage coal and a hard wipe pad are sometimes used), vibrating, and for small items centrifuging (such as with a die in place that is sized according to the desired amount of coating gauge to be applied). While and directly after the finishing process is going on the material is rapidly cooled using different methods to include cold water, high pressure air knives that use nitrogen to form and cool the material. The cool water is aided by chillier units that decrease the temperature of the water before sending it to a quench tank where the material is directly cooled by immersing the completed material directly in the cold water. In many applications the product is also immersed in a wax based substance, applying a light coat to aid in the product being separated when at the end of the continuos run or in use later.

9) Inspection: The inspection process of galvanized material is the simplest and most important means of assessing the quality of the galvanized zinc coating. The inspection process uses some standard testing such as tensile strength, yield strength, hardness, elongation, stress/stain, form/condition, thermal conductivity, electrical resistance, coating weight/gauge, and most importantly the appearance of the finished product. The appearance of the galvanized coat demonstrates the relationship to the coating quality.

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