Hot Dip Galvanizing Line Producing GI And GA Coils For Automotive Applications

In order to minimize the problem of autobody corrosion, steel sheets for automotive body panels have undergone enormous changes from the conventional cold rolled steel sheets to coated steel sheets.

- Sanat Bhaumik

As an answer to counter corrosion caused by road salt in countries of cold climate, various types of coated steel sheets were developed and used since the second half of 1970s.

Coated steel sheets which are used in automobiles must not only provide corrosion resistance but also satisfy to variety of other performance requirements like pres formability, weldability, phosphatibility and paintability.

For automotive skin panels the major car makers in North America and some in Europe use electro-galvanized (EG) sheets with comparatively heavy zinc coating. In contrast, car manufactures in Japan use mainly galvannealed (GA) steel sheets which have a zinc-iron alloy coating.

At present, the use of galvanized steel in automobile body in India is only around 7 percent while around 80 percent of cars manufactured for exports have galvanized sheet body. A survey reveals a good correlation between the defects in automotive body and the age of the vehicle. Body parts close to the road are most prone to defects such as blisters and surface rust. This survey also reasonably establishes that the conversion of car body panels manufactured in India from painted cold rolled steel to painted galvanized steel will significantly improve the corrosion performance. It is now a matter of time that increased use of GI/GA strips in car manufacturing in India becomes a reality.

Special features for an automotive CGL

These following equipment are required additionally by an automotive CGL over and above the other standard features like Double pass Payoff, Loopers, Welder, After Pot Cooling, Tension Leveling, Chemical Coater, Recoiling, etc. for a Conventional Galvanizing Line targeting construction & appliance markets:

1. Electrolytic Cleaning Section

2. Pickling Section after cleaning

3. Annealing Furnace with Heating, Soaking and Rapid Cooling Sections