Hot Dip Galvanizing – Principle Of Galvanizing ,types
What is Galvanizing :
Galvanizing is the process which employs an electrochemical action for providing a coating of highly corrosion resistant material on the surface of another metal. The galvanizing process is widely used for providing a coating of zinc on iron and steel.
It is very much low cost process and widely used for corrosion resistant coating on sheet metal, household items for daily used made from iron and steel e.g. buckets, tubs and other containers. Galvanized is also done on machine parts, tools, ships tanks and wires etc.
Galvanized pipes, metal sheets and wires are probably the most popular galvanized items which find wide applications both in industrial use as well as in articles made for domestic use. There are number of techniques can be employed for galvanizing of zinc to the metal surface.
Techniques Used in Galvanizing :
The following are the main techniques used for galvanizing of zinc:
It is the cheapest of the galvanizing techniques employed in mass production.
Hot Dipping Galvanizing Process :
The first step in applying this process is thorough cleaning of the items to be galvanized. This involves decreasing etc. depending upon the condition of work-surfaces. The main idea is to obtain an absolutely clean surface. If the item to be galvanized is sheet metal, it is annealed after surface cleaning and then cooled in an oxide free atmosphere. The sheet is then dipped in the bath.
If uniform thickness of coating is required then sheets are drawn through set of rollers immediately following the coating process. This process drives away the excess zinc and allows only the required amount of zinc to remain on the surface. Without this process the coating thickness cannot be controlled. This is followed by drying, and then the sheets are ready for shipment.
In another method of galvanizing instead of dipping the article in hot zinc bath, hot zinc is made to flow over the surface of the article. This process suits well for galvanizing extremely large surface of iron and steel sheet.
Applications of Galvanizing:
1. To galvanized sheet metal.
2. To galvanized house-hold items such as buckets, tubs and other containers.
3. To galvanized machine parts, tools, ships, tanks and wires.
4. Metal pipes and wires are most popular galvanized items which find application in industrial use as well as in articles made for domestic use.
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