Galvanization or galvanizing is the process of applying a protective zinc coating to steel or iron, to prevent rusting. The most common method is hot-dip galvanizing, in which the parts are submerged in a bath of molten zinc.

1. Zinc Production & Galvanizing
Department of Material
Technology 2015/16
Rajarata University of Srilanka
(Sample Presentation)

2. Introduction
1. Chemical Formula - Zn
2. Atomic Number - 30
3. It Is Bluish White To Silvery-gray In
Color
4. It Is Hard And Brittle At Most
Temperatures

3. Process of Zinc Production

4. ROASTING
 The Fluid Bed Roaster is used in the process of zinc sulfide concentrates.
 Zinc sulfide concentrates introduced directly into the roaster.

5. LEACHING
 The Zinc Calcite from the roasting process is fed for the leaching process
 Continuous pH monitoring is facilitated by submerged pH
 cells in controlled tanks

6. PURIFICATION
 Zinc oxide is converted into Zinc Sulphate by adding Zinc Dust.
 In purification plant, metallic impurities such as Cd, Cu, Ni, Co are also
removed

7. ELECTROLYSIS
 In electrolysis, plant Zinc is recovered from Zinc Sulphate
 After the purification process, Zn is converted in zinc anode and zinc cathode
bypassing the electric current

8. MELTING AND CASTING
 Automatic System for Melting and Casting are used in making slabs &
Jumbos Casting Machine.

9. CLEANING
The hot dust-laden roaster gas is cooled and dedusted through the Gas Cleaning
system.
Waste Heat Boiler
Hot Electrostatic Precipitator (ESP)
Wet Gas Cleaning
Cooling
De-Dusting
SO2 Gas Scrubbing
Wet Gas Electrostatic Mist Precipitator (Mist EP)
Mercury Removal
Zinc Oxide Scrubbing
Flue Gas Desulfurization (FGD)

10. SULFURIC ACID
 For the treatment of Sulfur Dioxide (SO2) in the roasting off-gas, by passing
through the Gas Drying Tower, the Sulfur Dioxide (SO2) Gas(SO2), cooled and
saturated with water vapor, comes in direct contact with concentrated acid.
Sulfuric Acid(H2SO4) of this concentration is very hygroscopic (absorbs waters)
and the gas is practically free from water vapor after leaving the Drying Tower.

11. USES OF ZINC
 1. As An Anti-corrosive Agent.
2. Process Of Galvanization, Like Light Posts, Metal Roofs And Car Bodies.
3. Also Used As An Anode Material In Batteries.
4. Coating To Protect Iron And Steel.
5. ZnO Is Also Used In Rubber To Protect It From UV Radiation.
6. Alloyed Zinc Is Used In Pipes, Instruments, Hardware And Water Valves

12. APPLICATION
 AUTOMOTIVE
 BUILDINGS AND CONCENTRATION
INDUSTRIES
 HOT DIP GALVANIZING
 ZINC CASTINGS

13. ABOUT GALVANIZING
 Galvanization or galvanizing is the process of applying a protective zinc
coating to steel or iron, to prevent rusting.
The protection is two fold
• Physical protection from moisture and air
• Electrical catholic Protection

14. Galvanizing Methods
 Hot dipping in molten Zn (HDGI) thick coat
 Continuous sheet galvanizing
 Zn paint or Zn spray – thin coat, weak bonding with the steel surface
 electro-galvanizing – thin coat, strong bonding better finish

15. Step in HDGI Process
 The material generally used is Aluminum, silicon and phosphorous killed steel so
that no oxidation occurs during solidification.
 Abrasive Blasting: the process of using powerful steam of particles,
available in varying hardness. To remove residue and contaminants from
the steel surface to prepare for galvanizing.
 Casting cleaning to remove organic impurities.
 Passing the metal through a molten bath of zinc at a temperature of around 460
C.
 Further reactions: the pure Zinc reacts with the oxygen to form zinc
oxide, which further reacts with carbon dioxide to form zinc carbonate, a
usually dull grey, relatively durable material that stops further corrosion in
many circumstances, protecting the steel
 .

16. Duplex coating
 The duplex coating is liquid or powder paint over galvanized surface done to provide for synergistic
protections.
 Is ten times more abrasion resistant
 Is eight time more chip resistant
 Offers 20 times more edge protection
 Excellent long term corrosion protection
 Attractive appearance and ultimate colour variety
 Environmentally sound process.

17. Advantages and Disadvantages of HDGI
Advantages
 Smooth and uniform coating.
 Sharp edges and corner are protected optimally.
 Stress release internal
Disadvantages
Limitation of the product size

18. Applications of HDGI Steel
 Roofing and walling
 Safety barriers
 Handrails
 Consumer appliances
 Automotive body parts

19. Electro galvanized steel
 Electrolytic deposition of Zn on surface
 Often used in automotive manufacturing to enhance the corrosions performance
 this coating cannot stand high temperature
 Zinc coatings, whether electro galvanized or hot dip usually require chromate conversion coating to deter white
rust.
 For fabrication that needs to operate at high temperatures sulfa mate nickel plating is used
 Electro galvanized coating are susceptible to zinc whiskers
 Zink coating in electro galvanization is mentioned in terms of thickness of the layer

20. Galvanizing