Why Car Bodies Are Not Made of Stainless Steel ?

I do not agree with you. Material cost of car's body is a very small fraction (It is power train, amortised cost of tooling and development, safety devices, upholstery, electrical and electronics, hydraulics etc. which takes lion share of a car's cost)

When automakers are trying to squeeze pennies out of switches on the dash, saving even a few dollars on sheet steel is a big deal.

In addition to that, galvanization and other metal treatments and paint systems used to coat steel are getting so good as to render the issue of rust all but non-existant.

Just look at some of the new car warranties for paint and body defects as proof.

Since you reject the answers already given, why do YOU think car bodies are not made of stainless steel?

Why not GFRP as a body material?

Well you can buy a DeLorean, then. Now live and let live.

Too expensive.

See DeLorean.

Then go the way that you want to go. Agreement isn't actually necessary here, Mildred.

Passivation combined with pickling is very durable (much more than gloss of paint). I did not understand "Any contact with iron bearing material will call rust" - SS does not rust. Sand papering does remove scratches in SS too. Welding SS calls for just SS electrodes - nothing more. Any hardening which occurs during cold working (typically repairing dents) can be easily undone by localised flame annealing.

The only valid point which seems to be going against SS body panels is sticking of paint to the surface. But with SS who wants painting. Ok, if painting is such a big issue, then why not at least make floor panels, gas tank of SS.

What about floor panels & gas tank.

Why would you want to use stainless steel?

Still too expensive.

If the vehicle were designed to last 30 years, then maybe.

As Doorman suggested what about GRP, or blow molded polyethylene?

I just photographed a 1983 Delorean in a parking lot by my office. It's there every day. The SS body looks great, like new. I can't attach the picture, sorry.

It is all about cost.

Finally! This car is 31 years old. No dents, no rust. Taken today.

Let me guess, this is your vehicle in Arizona. Here in summer ocean salt spray and winter rock salt coated roads Long Island NY the corrosion is a little bit more of a problem.

Nope, not mine. I can't afford the flux capacitors.

Welding SS does call for more than just SS electrodes. A conventional "body shop" (as they're called in North America, which induces sniggers in some other locales) is likely well equipped with MIG welders that can easily handle SS wire- unlike aluminum, which usually requires an additional spool gun.

But welding SS panels with conventional mild steel techniques leads to crystallization on the backside of the weld, giving a weaker joint that is much more susceptible to fatigue than a mild steel weld. And with the lower thermal conductivity warpage can be more of an issue- not to mention Bondo showing up pretty easily on the finished job. Or were you thinking of going back to lead filler?

the thought of car bodies made of stainless steel came to my mind when i first began to understand cars and later on when we owned one, the problems associated too. where i live it is impossible to keep the paint of the car intact. your car gets scratched pretty often. there is always mud in the path which get stuck in the joints which start rust. rust is like cancer once it starts its impossible to stop. when i see rust on cars i always wish their bodies were made of stainless steel. so you didn't had to worry about rust while driving through muddy paths. stainless steel is not that much expensive. most average income families own cars because they need it. and they need it to be durable. specially in humid and muddy situation. the only reason i now understand why automotive manufacturers don't make vehicles with SS bodies is that the selling rate of vehicles would decrease because people would not need to buy new cars that often.

compare the flexural modulus of stainless steel with carbon steel, and see which one wears out first?

There are some issues with body repair on SS cars.

SS body panels will work harden when trying to rework into the original shape.

Filler cannot be used. Paint adhesion was also an issue for the buffed SS panels

Properly galvanized and coated CS panels are a better choice.

http://en.wikipedia.org/wiki/DeLorean_DMC-12

they are!

You for got these.

Because most customers do not see any value in stainless body parts. Some Jeep owners do see a value in stainless steel parts so an aftermarket exists. This is probably because of the common off road use of many Jeep owners.

Stainless steel only REALLY works on vehicles with Flux-gate Capacitors and 1.6 GigaWatt engines going 88-mph going back to the future.

It's really not necessary with modern technology used in auto manufacturing. I've owned new cars since 1995 and all of them have gone nearly 300K miles with no rust issues. I don't see SS as solving any problems.

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How does SS hold up to road salt?

Without knowing the specific grade of steel one cannot pass judgment on the corrosion/salt resistance of it.

My only comment is, much better than carbon steel. Road salt brings abrasion with it in the form of many projectiles and accumulated moisture that speeds the process. I don't think cold weather inhibits corrosion very much.

We used a 1,000 hour salt spray test, per some ASTM test that I have forgotten, during my materials engineering days. But, that ain't road salt.

My opinion is SS is only worth the cost for LONG term use.

According to Wiki, the DeLorean DMC-12 body is made of SS304 (A2 Stainless). Just says brushed, I suppose #4 finish.

Aluminum is better, lighter, cheaper.....a lot of cars nowadays have aluminum body parts....and plastic....Lighter = faster/cheaper

The new Ford F-150 has an aluminum body and saves 700 pounds of weight in the bargain.

No doubt there are costs involved, but in the long run, it's better than stainless steel.

My old Ford F-150 has plastic (GRP) rear fenders. They can't be repaired easily and at $1,000.00 a side they aren't cheap to replace if damaged.

My Mustang has an aluminum engine, hood, and I think fenders, as well as wheels....They have other aluminum parts available such as drive shaft, front pulley, lower control arms(I have those as well), every time I look I find something else...I'm convinced that's what makes the car so responsive....A few hundred pounds makes all the difference...The new F-150's should be legendary...with a 5.0 of course....

"The new F-150's should be legendary...with a 5.0 of course...."

Thanks for the warning! I'll keep an extra eye out for fishtailing trucks.

I discovered that the rear hatch on my '02 Suburban is aluminum because my magnet flag wouldn't stick. I believe they made the hatch aluminum to save weight and reduce the load on the gas springs that prop it open. I wished they made the rocker panels and quarter panels out of aluminum or stainless because I'm getting rust through issues on a 12 year old truck with only 210K miles. Looks like I'm going to be learning how to TIG weld sheet metal now. The cloth interior has held up well. They did get that right so I'm in no rush to replace the truck. Fixing transmissions and differentials is easy stuff. Body work is a *itch.

You may find MIG/MAG better for body welding as working above your head with TIG may be painful, but still possible I believe.....I have never seen a TIG welder working on his back though.... Not that I have seen that many!!!.....there are videos of how to do it on the web....

I would like to teach myself TIG one day for other reasons, till then I'll stay with MIG....

I have welded stainless and steel with resounding success and a lot of fun, next stop is to buy a welding gun one day and try MIG/Aluminium.....or Aluminum if you prefer!

Great hobby.

MIG is definitely more practical (not better) for bodywork, but I've seen coveralls set on fire when spatter landed in a pocket while welding in a wheel well. TIG is a totally different story with next to no spatter when done properly.

I've welded joints on 304SS pipe runs 18 feet in the air- on my back, because they were 7 inches below the ceiling insulation, and to ensure penetration I had to prop a mirror above and weld in the reflection (this is awful with auto darkening helmets- you have to light off the arc on the side to activate it first if your amps are low, otherwise they tend to take forever to trigger) on the tops. Most of it except the outside pipes was done completely on my back on the lift, as it was easier than straining my neck standing up and welding overhead. Would I do that with MIG? Not a chance!

I like welding with TIG. I especially like the control and lack of spatter. I've tried MIG welding and I found it harder on sheet metal than the TIG. Since all the stuff I need to do is easy to get at, I think this will work out. I'm just a novice welder so I'll take my time.

You said "I'm just a novice welder so I'll take my time." I an only say "me too!"

As sort of a corollary to the "take my time with <welder> fill in the blank", my well-seasoned dad has a favorite saying about power tools in general.

He is fond of saying, "Power tools allow you to make mistakes faster."

One time I decided to use hand tools while doing some cabinet work. I didn't want to listen to screaming machines in a small room. I got the job done. It didn't seem to take longer. I made fewer mistakes. And it was a lot safer.

Thanks for sharing!!

Yes! Cost and weight. Whether OP agrees or not. (And weight goes back to cost, like gas mileage, speed, consumer's desires... etc.)

Aluminum = beer can bodies!

Did John DeLorean once say "you can have it in any colour you like so long as it is silver"?

Mr & Mrs Car Buyer like pretty colours and painting over SS is such a waste.

No, he said, "Anyone looking for a good deal on some cocaine?"

Mostly price! There are many other materials more suitable and less costly to use. St Stl requires more labor to work with and the material is heavier than others such as plastics and specialty materials such as carbon fiber. The reductions in weight, labor and initial costs all add up weight wise. This lowers the mileage of the vehicle which makes it more expensive to operate. Despite the lowers costs for other than St Stl . the operating expenses are dramatically higher. At $4.00/gallon for gas, the difference between 20mpg and 17mpg is $0.04/mile. For the first 100,000 miles the savings is $4,000 and that does not include differences in initial pricing. For a 250,000 miles car that is a savings of $10,000. If there is a greater differential between the mileages the savings is greater. Get the right car and you may save the cost of the car over it's life!!

Good Luck, Old Salt

Because a '54 Ford would cut through it like butter.

You sound like someone with bad experiences of 20+ year old steel cars......once the rust is in, its difficult to stop....Been there, done that......

I personally feel that GRP, properly made, is a good safe alternative.....but so many are made down to a price and not up to a quality....as some boat hulls are too.

I have a small amount of experience with Davrians and Quantum sports cars many years ago and in accidents the "opposing" vehicles suffered far more damage than the GRP car did, because both were designed and made correctly....they do also eventually crumple if the opposing speeds are high enough, but shrug off fender benders far better. Just scratches usually.

Adrian Evans (designer & builder of the Davrian) once took out all of the side panels of a London double decker bus with his prototype and only had to fill a small area about the size of my hand on the Davrian and respray the whole wing....the bus was really expensive to have repaired!!

The only really bad point with normal GRP, if you have a petrol engine fire is that its not good in a fire. But it does give you a good length of time to get out, assuming you are awake... But that fire problem can be helped with modern fillers and changes to the resin mix I am told.

An article I found talks about the fire hazards and mentions that once cured, a large source of heat is needed to cause damage to GRP. See here on page 3:-

Fibreglass

I have also to say that I have never seen a well built GRP car go up in flames myself, mostly only Reliant 3 wheelers.....

Although it really does depend on the particular alloy, SS does not offer the rust-free performance that many think. I have seen 0.25" of SS316 rust through in less than 6 months when exposed to the combination of sulfuric acid rain and chloride ions (any seashore with a coal fired power plant nearby). You can use the higher nickel, or exotic, alloys and slow that quite a bit, but the cost goes up and the performance usually goes down.

Cars have the ever-higher bar of average fleet mileage requirements, so aluminum or fiber reinforced plastics are the better choice for present.

Not that it didn't happen in a few cases, but a brine solution of sodium chloride and oxidizing materials from combustion products of gas flame (open evaporator) has a corrosion rate of .0418 inches per year for 316SS. This corrosion is primarily moderate pitting (maximum depth of pits from 0.005 to 0.010in per year) and crevice attack (tendency to concentrate-cell corrosion). This information is from "A Guide to Corrosion Resistance, 304 316 317 "20" and Ni-O-Nel"; published by the Climax Molybdenum Co. div of American Metal Climax; 1961.

Could there have been other materials involved? My sailboat has a 316SS centerboard that has been in salt water from the early spring through the late fall and has shown no corrosion for over 50 years. Also the corrosion for 316 in salt water is primarily the "worm hole" type, very narrow but deeper than narrow. This is similar in shape to the hole a worm would create.

Good Luck, Old Salt

I did say "acid rain." When you burn high sulfur coal or oil (we have a lot of that), you get (hopefully weak) sulfuric acid if there's any moisture in the air. Add a few chloride ions and Bob's your uncle.

Why car bodies are not made of stainless steel sheet.
Cost.

But do the reactors utilize garbage or dilithium? Hard to find unmarred flux capacitors theses days. DeLorean is the way to go if you want stainless steel. Don't hang around the beach too much, though.

Simple answer, the profit margin doesn't justify the use of stainless.

As to rust, let an HCl line open up in a room and see how much stainless will corrode from exposure to the the vapors. Also, those microscopes with there achromatic coatings are permanently fogged.

Some auto designers were standing around, drinking beer, and admiring the clay model they had just completed. One of them suddenly noticed something was missing. So he takes his beer can and shoves it into the spot where the tailpipe should be. The production model came with a tailpipe that looked like a beer can.

PJ (poor joke)

PSoH. Poor sense of humor.

You are welcome.

It's not a car but this type is quite popular as an informal vehicle here in the Philippines. 'Not as expensive as a car and fuel consumption is lower (can't say much for the emissions though). Safety wise...better leave that out. On the road, it's a pain for other drivers due to the reflections off its skin. Would I buy one? No way. (",)

regards,

Vulcan

This is one valid point against SS body. The reflection will be a pain to other drivers.

Easily achieved on GRP with Chrome painting!!

This one isn't even made of metal. No corrosion there.