[i74js]

Indian car manufactures are famous for their shoddy practices and use of galvanized steel is another aspect where they shamelessly cheat.

As per the international zinc association which is one of the largest industry bodies for zinc manufacturers and suppliers, Indian car manufactures use only about 3% of galvanized steel and in some recent launches the use has been increased to around 20%. The same company for export models use about 70% of galvanized steel.

On an average about 10-11 kg of zinc per car is consumed in western countries whereas in India it is between 0.3 - 2 kg per car except for few European players who continue to use the same grade of steel both for India as well as export markets.

The website link is

http://www.zinc.org.in/zinc-in-automotive/

Also, please read the corrosion performance survey - case study published by them. You will have to register to download the report

Equally interesting is the article published in Feb 2018

http://indiaeducationdiary.in/indian...y-compromised/


We are typically getting cheated almost at every front; be it undersized air bags, missing K-truss or non performance of airbags during accidents, and now the case of use of sub-standard "white body" of the car !

[AdiSolEn]

I think that not all body parts are made from galvanized steel. But even when they are made from galvanized steel, the places where welding happens, the zinc coating in that region is destroyed. This part, if exposed to the elements, will lead to corrosion. VW has developed a special joining process specifically for this reason, that achieves the bonding at a temperature that is lower than the melting point of zinc, and hence their bodies do not have weld areas with the zinc coating destroyed! This technique is already in use for the Polo and Vento in the Chakan plant!

[Aroy]

Using Galvanised steel helps in corrosion prevention, but it is just the first step in a process. Any weld on galvanised metal will strip the protective zinc coating, hence post welding treatment is required.

https://www.galvanizing.org.uk/weldi...vanised-steel/

On the whole for large area sheets, galvanized steel will add another step in corrosion prevention, but remember that all welded areas will have to be treated further, else the rusting will start there. What will really deter corrosion, is to galvanise the body shell post welding prior to painting, but that will involve a huge outlay in a dedicated galvanising plant, which I doubt any but large volume player will be able to afford.

Even after using galvanised steel, auto manufacturers do phosphate treatment during painting process, hence one cannot really claim that body members made of ungalvanised sheets are inferior, considering Indian conditions.

[norhog]

Originally Posted by MaxTorque

Like everyone said here, Galvanized steel will give superior corrosion resistance which is mandatory in European, US weather conditions. Generally, European car manufacturers are hesitant to deviate from their proven methods, that is the reason VW and Fiat still stick to Galvanized steels. That explains why they are expensive and their models are not so cost effective.

In India, I would say almost all mass-market models are made of cold rolled steels. The first process of painting is pre-treatment. Which gives the body necessary anti-corrosion property. To explain it a bit further there are various stages in pre-treatment

1. Degreasing - A hot alkaline chemical will be sprayed over the body and later the whole body will be immersed in the tanks for 2-3 minutes. The number of stages varies from manufacturer to manufacturer.
2. Activation - It basically makes the cleaned body shell ready for next and the most important process by making micropores in the body shell so that the next process is effective.
3. Phosphating - This is the most important process where the body shell gets a coating of Zinc Phosphate all over the body. The micropores generated in the previous process help to accelerate the phosphating process and will give better bonding between the body shell and phosphate coating. If this coating is damaged then the corrosion will start in no time.
4. Rinsing - There will be many washes between each stage as per the process requirement.
5. Electrocoating - The body will be connected to a negative terminal of a powerful rectifier and the paint will be charged as positive. This process helps bodyshell to get a uniform thickness all over the body both internal and external.

The whole pre-treatment and electrocoating process will take around 1.0-1.5 hours.

In the recent years, aluminum has become popular and many manufacturers have started using aluminum parts in mass-market cars. As of now, the whole aluminum body has been limited to performance cars.

This is a nice explanation.
I would request that along with process insights, if the persons in the know of the industry can share which car maker or model uses which process it would help the formers in making an informed descision on all things automotive.
One thing looks clear from the discussion above that VW, FIAT, FORD models sold in India are not different by way of body manufacturing process as compared to its export models.
So who does this differentiation...
Maruti, TATA, Mahindra, Hyundai..

Somehow I feel pain to see TATA in the second list..Just a personal opinion.

[MaxTorque]

I don't think any of the manufacturers you listed are using special body panels for export models. Because it is very difficult to control the mass production process unless they have separate plant/shops.

But they may have additional processes like cavity waxing, sealing etc. to add rust prevention.

In my opinion, the normal cold rolled steel with CED coating and painting process will give decent rust protection. In case of scratches or exposure to corrosive environments, the body shell may start corroding.

[SCORPION]

Originally Posted by norhog

https://auto-economictimes-indiatime...ody%2F49414233

This article sounds more like a rant by the International Zinc Association to sell more zinc in India rather than a real concern that Indian cars are more prone to corrosion because they do not use galvanized steel. To me it resembles a cheeky attempt by an industry lobby to sell their product. For instance the Olive oil lobby stating olive oil is the best oil for health, the coconut oil lobby claiming coconut oil is the best and so on.

Mumbai, for that matter, any coastal area has higher levels of salt and moisture in the atmosphere. Badly maintained cars are bound to suffer under these conditions. I wonder which 5000 cars were surveyed, for him to come to that conclusion. Salt is the biggest enemy of steel.

In what way does galvanized steel reduce the weight of a car? High tensile steel might. But galvanized steel?

Most of these discoveries of things missing or being different in Indian versions remind me of the famous cartoon scene where a cartoon character runs straight off a cliff into thin air and returns without falling down. He doesn't know about gravity. Next time he runs off the cliff, some one tells him about gravity (or he reads about it, can't remember). This time he drops to earth like a stone!

Similarly, here, everything is hunky dory with the cars until someone discovers something is missing, or is different from International versions, and, suddenly, these cars become untouchables and something that should be abhorred.

Cars need to be maintained and taken care of. They need to be serviced at regular intervals. Beadings should be checked, maintained or replaced and water should not be allowed to collect in spaces. The underbody has to be washed at regular intervals. Dirt and muck collection can lead to corrosion. An owner has to do his part.

Ship hulls are subjected to the toughest conditions as far as corrosion is concerned. Ship steel hulls are not galvanized. Instead they use high quality paint protection coatings. Galvanic protection is only provided for the portion of the hull that remains under water in the form of cathodic protection using sea water as the electrolyte. But that is only possible on the underwater section. The rest of the steel is exposed to wind, sea water and sea sprays. Large amount of salt is deposited all over the steel creating an ideal situation for extensive corrosion. But the Marine paints are so good that unless there is contact damage or paint peeling, the underlying steel remains in excellent condition for more than 5 years before it needs a touch up. To top it, ships are not even painted in paint booths. Painting is carried out in open yards with only the atmospheric moisture content and rain as a limiting factor. 5 years in a marine environment is probably equivalent to 50 years on land.

Now, you might find it unfair to compare a ship's hull to the sheet metal in a car. But what I want to put across is that galvanization is not the only way to protect steel.

Different grades of steel offer different levels of protection against corrosion depending on the composition of the steel. Good metal treatment methods, coatings, primer and top coat is sufficient to prevent corrosion. Maintenance has to be carried out as per the manufacturers recommendations post purchase. Contact damage and any portion of the cars body where the paint has peeled off, for whatever reason, has to be touched up properly with proper surface preparation, primer and top coats.

Conditions abroad may be different to conditions in India that warrants galvanization. Cars made in India under Indian regulations may be in many ways inferior to their counterparts in other countries and may have consequent draw backs, safety issues and failures. But apart from known issues like the one in the earlier FRP bodied Bajaj Tempo Traxs, I don't think there has been any consistent cases of issues with the body or corrosion in Indian made cars that should warrant statements saying that they are prone to corrosion related failures just because some of them may not be galvanized.

[rajshenoy]

My Ertiga had a deep cut on the door over 5 years ago and i always park in the open(sun and rain) almost 24x7. There is not even a hint of rust on the exposed metal area which makes me believe the sheet metal is definitely galvanised.

Not sure if they cut corners on low end cars but my hunch is that galvanised steel is used on most of the visible body parts.

[SnakemanJohny]

Indian car bodies are not generally galvanised. Some luxury manufacturers may sell their galvanised models in India, but general makes are not, especially Maruti Suzuki. Sheet metal quality has improved, is given a phosphating coating or some such, before the painting process, or surface treatment & painting techniques have improved beyond what Hindustan Motors and Premier Auto Ltd. used to do earlier, so generally cars do not rust as fast.

Another reason some of you may not have experienced rust in nicks or scratches on your cars is that the scratch may not have penetrated to bare metal. Automobile steel sheets have a thin 'skin' of surface treatment to resist corrosion -- similar sheets are also used in other consumer appliances.

I have worked in the Steel Authority of India Ltd (SAIL), and Maruti buy most of their sheets from SAIL. Micro-alloys have been developed in the steel industry to supply thinner sheets to automobile and other industries to resist corrosion -- but generally galvanised sheets are not purchased by them.

My 1964 Nissan Patrol (Jonga, but made in Japan, not Jabbalpur ) has such high quality of body sheet that if the paint is shaved off the body still shines for a few months before catching rust. If you see the Indian Jonga, the mudguards would rust through in two years, and spray dirty water on those inside -- so low was the quality of steel sheets used by VFJ.

Some of you are right in saying that galvanised sheets would rust at welding joints. But to counter this, the welded/finished car body is galvanised, not the sheets before manufacture.

The old technique of 'hot dip' galvanising , where the sheets/ any finished product used to run through a bath of molten zinc, has been mostly done away with. That gave a thicker zinc coating (more protection) but at higher cost. The preferred technique now-a-days is electroplating, lower costs with acceptable levels of protection. It all depends on what grade of corrosion/ rust protection you want -- electricity suppliers, railways etc. still want hot-dip galvanising for their outdoor equipment -- and manufacturers have to comply or not supply !
Similarly, some parts of cars used to be hot-dipped earlier. An example may be the clutch pressure plates in earlier cars, which were not changed every time the clutch lining plates were. In modern cars, complete clutch plate-pressure plate sets are changed every time, so the plates are given a thinner zinc chromate coating (electroplated).

Galvanised car bodies would be better in most of India except the dry central region where rust invasion is lowest. Particularly in the coastal regions with high salinity AND humidity, at least the underbody should be galvanised, with double strength for the mudguards (if possible). Same with North East India, where rainfall and humidity are high, if not salinity. So what if our roads are not 'salted' in winter, we have enough salt in the air !

What the fellows mean by saying that galvanising would save weight, is simply that thinner sheets could be used. But the sheets have to be so thin that the extra weight of the zinc (even a few microns), would be lower than the untreated sheets. That way, I think we are better off without galvanising !

[volkman10]

Government may force automakers to use 70 per cent galvanised steel in car body

Automakers in India use only 30% galvanised steel for vehicles to be sold in the domestic market, but the percentage rises to 70% for the same model if it is for export

The global average is 50%. The proposal — under corrosion prevention rule for motor vehicles — pertains to cars made in India and costing less than Rs 10 lakh.

the move is part of the ministry’s thrust to establish standards that will enhance road safety.

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