[norhog]

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

I was under the impression all modern cars sold in India use galvanised steel for its bodies. But this article states otherwise.
Galvanisation process is mandated by regulation abroad hence cars sold in foreign shores, while being made in India, use galvanised steel for the body manufacture, where as same model of cars sold her do not use galvanised steel for its body.
So what is going on.!!
Which cars sold in India have galvanised steel used for its body and which don't.?
And how much of a difference galvanisation makes.?
Can modern polyurethane paint more than compensate for lack of galvanisation.?

I could not find a suitable topic so started this thread. Mods, if there is a suitable thread, kindly merge it there.
persons in the know of this topic may please shed some light on this..
Thank you

[Shreyans_Jain]

All cars are supposed to be galvanized. I distinctly remember the Tata Nano documentary on NatGeo/Discovery. They showed the tiny car being put through the zinc bath.

If the Nano was galvanized, I'd like to think all of them are. But of course, this is India, and you never really know...

[niteshbids]

I'm pretty sure that a lot of manufacturers do not use galvanisation. Use of galvanized steel finds a place of pride on VW's brochures and website. If this was a norm, this wouldn't be the case.

[Subby]

I happened to work in Bhushan Steel indirectly as a service provider. Bhushan produces Galvanized Steel sheets by Cold Rolling Mill process. Maruti used to buy those products for their cars.

So it could be a norm to use galavanised steel for car body as a standard manufacturing practice by Maruti. However exception could be there.

[norhog]

Thank you Subby, you are the person in the industry so have deep knowledge.
But the fact mentioned in the article that cars for export markets use galvanised steel and the Indian do no, seems unfair at first, then odd.
We all know current generation cars don't rust like the ones in our childhood, back in the 80s.
I remember Premier 118NE was worst. Had it in the family when we were in kids around 9th or 10th standard up until we were in college. (1994).
The area below front doors almost every year would rust away.
Never see rusting like that since then in newer crop of cars.

[arjab]

Legislation plays an important role here. It is not mandatory for OEM's to sell cars in India with galvanised body-in-white's.
The corrosion resistance criteria in India is pretty low and vehicles with more or less good paint and primer quality can pass these tests without resorting to galvanisation.
This has in fact now emerged as the favourite area of cost cutting. Another area of cost saving you will see is the recent trend in the elimination of rear fog lights, because in India it's not mandatory to have a rear fog.

As far as I know, most of the imports, like the BMW's, Merc's, Audi's, Jag's etc are fully galvanised. Amongst the mass market brands, the present range of Vento's, Polo's, Rapid's are galvanised (VW offers a healthy anti-corrosion warranty).
Fiat, starting from the Palio had a full galvanised bodyshell. Including Linea and Punto. Ditto with Jeep. Ford also uses extensive galvanised sheet steel.

Other OEM's are suspect. They definitely do not use full galvanised bodyshells, maybe some localised areas, like wheelarch inners etc are galvanised.
Chances are remote with respect to popular entry level hatches submission to galvanisation though. In all probability they do not.

The easiest way to find out if you categorically question an OEM about anti-perforation/anti-corrosion warranty. Those who do not offer coatings to protect your vehicle from the tin-worm will be loathe to answer your queries, whereas those who do can use it as an USP in their sales brochure.

And yes, all models of the same vehicles exported are fully galvanised. Otherwise they will not be able to pass homologation in the destination country and neither will anyone buy the cars.

[Rahul Rao]

I remember tempo traveller adds in the 80s where they used to show the entire body shell being dipped in one tank after other.
That was the first vehicle in India to be galvanized. Later on Tata also started with the 407 cab.
Among cars, I remember that when we used to open an Ambassador inside panel, the frame and lower part used to be different colour, and outer skin a different colour.
A sheet metal joint used to be visible from inside which was not seen from outside, on asking the mechanics used to say body structure, and lower half of doors is galvanized to prevent rust. I dont know weather this was OE, or aftermarket, as cars those days used to be stripped down and rebuilt every few years, and duplicate parts and body panels were very common.
As far as I know cheaper cars are made from galvanised steel sheets, the better ones made from sheet metal and the shell galvanized after forming is complete.

Rahul

[AAD]

Originally Posted by norhog

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

I was under the impression all modern cars sold in India use galvanised steel for its bodies. But this article states otherwise.
Galvanisation process is mandated by regulation abroad hence cars sold in foreign shores, while being made in India, use galvanised steel for the body manufacture, where as same model of cars sold her do not use galvanised steel for its body.
So what is going on.!!
Which cars sold in India have galvanised steel used for its body and which don't.?
And how much of a difference galvanisation makes.?
Can modern polyurethane paint more than compensate for lack of galvanisation.?

I could not find a suitable topic so started this thread. Mods, if there is a suitable thread, kindly merge it there.
persons in the know of this topic may please shed some light on this..
Thank you

The reason most manufacturers offer Galvanised steel bodies in Western Countries and Japan, Korea etc is due to the fact that during winter times, these vehicles encounter salt in the highways which is sprayed by the authorities to make the snow melt faster. During high speed driving on such roads, the salt mixed with melted snow will stick to various underbody parts and cause corrosion.

Regarding the ads that one sees in India about dipping the entire vehicle body in zinc bath relates to the painting process which involves rinsing, degreasing, passivation before the paint application by electrostatic deposition method.

The above comment is based on my understanding of the subject.

[norhog]

Thank you for the replies.
So in India, as discussed above VW, FIAT cars are using galvanised body.
What about other's.
Can there be a list so we Teambhpians can make a informed choice when taking descision on our cars.

[vikram_d]

All steel sheets used in the auto industry are pre-galvanized. If this was not the case our cars would be getting corroded in no time at all irrespective of how much paint it had on it.

This is just a reference link.

http://www.tatasteel.com/products-so...motive-steels/

PS: I kind of doubt the authenticity of the article mentioned above. Cold rolled steels start corroding in no time at all. I use un-protected cold rolled sheets day in and day out in my manufacturing business and I know how quickly they start corroding.

[Motard_Blr]

Just to clear up some confusion, the term "galvanised steel" means that the steel is coated with zinc. This coating may be done by various processes (chemical, electrolytic, hot dipping, etc.).

The coating that all car bodies are given is called cathodic electro-deposition coating. It is also called electrophoretic coating, CED coating or E-coat.

It is a primer coating that is electrolytically applied. A giant metal tank filled with the water-based coating is made the anode in the electrical circuit. The car body is made the cathode. The solid particles in the coating are attracted to the conductive metal of the car body and stick to it. The liquid penetrates all the nooks and crannies and the solid particles stick almost everywhere. Once the coating is done, the excess material is drained out and rinsed. The car body is then dried and baked to cure the coating.

The coating is generally a mix of polymer-based material (epoxy, acrylic, polyurethane, etc) with zinc and other metal compounds that help in protecting against rust. Once cured, the coating sticks extremely hard to the bare metal. So the protection against rust is both from the physical barrier and chemical action.

Maruti introduced this process in India with its cars and it was a revelation! In addition to being a revolutionary change in performance, reliability and user-frendliness, Maruti cars didn't rust the way Padmini or Ambassador cars did and also didn't require any special care.

[anshumandun]

I'm not from the automotive sector so I don't know for sure but from my metallurgy background, I think that all manufacturers are using galvanizing process, at least for the painted parts. To get a good paint finish and quality, galvanization is mandatory. Looking at the current cars with fairly decent paint quality and no visible rusts (like in older cars), its highly probable that all manufacturers do use galvanizing process.

It is possible that manufacturers do not buy galvanized steel and instead buy cold rolled steel and do the galvanizing process themselves before the painting process.

Even for the hidden steel parts that don't need to aesthetically good, good quality painting/powder coating is done to prevent their corrosion. Maybe the Indian manufacturers are avoiding galvanizing for these parts?

Galvanised steel also lowers the body weight and increases fuel efficiency, said IIT-Bombay professor AS Khanna.

I don't get this. Galvanized steel means that the steel has been coated with zinc. Then how come the overall weight is getting reduced? The only explanation is that manufacturers can use a thinner steel if they use galvanized steel and that would reduce overall weight. But if that was the case, everyone would just use galvanized thinner steel to reduce their cost. Galvanization is not a very costly process.

Khanna's survey of 5,000 cars in Mumbai, which has high corrosion levels owing to average humidity levels of around 60 percent, revealed that cars older than five years had rust formation and "bustering". Foreign-made cars fared much better in terms of atmospheric degradation, Khanna said.

What is the scientific definition of "fared much better"? Very vague sentence.

Indian car manufacturers use bare cold-rolled steel and its variants, while abroad it is mandatory for auto companies to use galvanised steel bodies.

Bare cold rolled steel will corrode in 2 weeks. Steel loves to get corroded.

The article has no specific and convincing arguments. I wouldn't take it very seriously.

As for the VW cars claiming galvanized steel and higher paint warranty, it's more to do with their better paint process and quality I guess.

[pranavGTI]

Originally Posted by norhog

I was under the impression all modern cars sold in India use galvanised steel for its bodies. But this article states otherwise.
Galvanisation process is mandated by regulation abroad hence cars sold in foreign shores, while being made in India, use galvanised steel for the body manufacture, where as same model of cars sold her do not use galvanised steel for its body.
So what is going on.!!
Which cars sold in India have galvanised steel used for its body and which don't.?
And how much of a difference galvanisation makes.?
Can modern polyurethane paint more than compensate for lack of galvanisation.?

I could not find a suitable topic so started this thread. Mods, if there is a suitable thread, kindly merge it there.
persons in the know of this topic may please shed some light on this..
Thank you

IMHO western countries adopt to use galvanised steel for automotive BIW is primarily to reduce corrosion i.e. under body corrosion. Starting December untill April (5 months) in any year the roads would be sprayed with salt to melt the snow and to prevent ice formation. The mixture of salt + water (melted snow) gets splashed allover the under body and wheels which results in fast corrosion if not galvanised. This is not the case in India except the regions near Himalayas. Hence it is not mandatory.

But the corrosion prevention is done in the painting process through phosphating as a base layer and painting on top of it.

[jinojohnt]

If a body part is not galvanized, it would rust within days of a paint chip. My 2008 Alto has scratches all over, but still doesn't rust. On the other hand, my Dad's 2012 Alto has started rusting at (door) scratches within weeks.

[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.