Underbody sprays are actually controversial. Up here in NH most people recommend against them. They can drive salty water into crevasses under the car where it would not normally go and it can sit there creating rot. People that I’ve known that did this generally had premature body rot.
Some people swear by them, I don’t.
That’s an area of some debate, actually. It really depends on the air temperature at the time. If the air temperature is low enough that the road salt doesn’t melt snow/ice, then the salt is not in an aqueous solution and therefore can’t do any damage - - until you wash the car and get the salt wet. What temp this happens depends on the exact chemicals your area is putting on the roads. Some de-icers are good down to 10 degrees or so. Some fail if you get below 20. Basically, if the streets are slushy, it’s probably a good idea to wash the car when you get home (washing it at the car wash is pointless, because you then have to drive through the salt to get home and you get a fresh coating of salt on your car again. So to do it right you need a garage that’s set up to wash cars. It gets expensive)
There’s a corn-based road “salt” that isn’t a salt that actually works better than normal road salt, and doesn’t rust cars. Unfortunately it’s something like 2x as expensive as the regular stuff so not very many places use it.
Even here in NH we probably only have a total of 20 days where the temps never get above freezing.
Here is the complete list:
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Yea, that is the total list.
That said, modern cars are generally far less likely to rust. Metals are better and the car design is better.
One note. Some owners fear rust, and want a rust prevention coating to protect there cars. Dealers love to accommodate the new owners. The sad part is that most of those cars that have been "rust proofed, are going to rust out because of that treatment. Those treatments compromise the anti rust systems that come with the car. That includes drains vents etc. Rust proofing blocks them and you get rust.Some auto mechanics shop are able to convert any car to carbon fiber bodies,but it could cost you a large amount of $$$$$$$…
Just to repeat myself. Cars are designed to "decompose"at a rate comparable to the mechanics they serve. Auto makers are not in the business of making rust free cars; they are in the business of selling cars for a profit. If their cars can have bodies that last a little longer than the competition, great. Too long, and it cuts into their own sales. Ask any long term ocean sailer or chemist how to deal with corrosion. Car makers in general “try” to do a pretty poor job and could do better at little or NO extra cost in manufacturing. Why would they ?
The bodies are just the visible part of the corrosion battle. Exposed mechanics take as bad if not worse beating in non visible areas.
Mufflers are now stainless because of govt. regulations, not the car company’s and Mida’s desire to save the consumer money. Same with brake lines, suspension components etc. So unless you’re willing to replace all those other components too, forget dealing with the body. Just treat it with oil in the seams, keep it clean and get 25 easy years out of it, but not a lifetime of actual use.
My Fieros’ Bodies Are Rust-Free. They’re Hard Plastic Above The Belt And Flexible Plastic Below. Underneath Is A Steel Chassis / Body Frame. My Steel Is Rust-Free As These Cars Are Not Driven In Winter.
CSA
30 years ago I’d say yes auto-manufacturers needed to do a better job of making cars not rust out so easily…
But now 30 years later…it seems they have. Even in the North East cars don’t rust out for years and years. Last time I saw my 98 Pathfinder it still had little to no rust with almost 400k miles. So why spend the money to make them last longer. Instead some companies should spend the money into making them mechanically more reliable.
New bicycle frames are almost exclusively carbon fiber or aluminum, or a mixture of the two. We have a saying in the bike business:
Light, durable, or cheap? Pick two. Goes the same way for car design, regardless of materials.
There used to be a British manufacturer (Reliant) that made metal framed, fiberglass bodied vehicles (went bust in 2002). This Scimitar and Robin (3 wheeled deathtrap) were fiberglass for sure. There were various versions of each. They were actually quite fun to drive (lots of power for a relatively light car). They had primarily Ford drivetrains, which ensured lots of highly available parts. They went from aluminium bodies to glass primarily for monetary reasons, I believe.
The old Reliants used to be sought after vehicles when I left Britain in 2000. Not sure about now.
Carbon fiber sets up a charge and corrosion when in contact w/other metals. Saw a carbon sleeved aluminum boom fail because of galvanic action.
Those Robins needed to be fiberglass, otherwise they’d be all dinged up after taking their first corner
Ford has a prototype, modular, aluminum truck chassis. The goal here is weight savings, not corrosion resistance though, as aluminum has corrosion issues that can be as bad as steel.
Aluminum chassis are not currently practical because the most cost effective fabrication means involve welding. If you weld high strength aluminum the strength is reduced so much that it is no longer effective in terms of weight savings and fatigue strength. This is why airplane fuselages are riveted, not welded. And the recent incident with SW airlines further demonstrates aluminums fatigue issues.
Aluminum does work well for cast parts such as engine blocks, transmission and differential housing though, as these parts do not require welding.
For exotic chassis materials, I don’t think we’ll see anything in the near term. Advance high strength steels is the direction the auto industry will likely go to reduce weight while retaining structural requirements. Higher strength steel = thinner parts to achieve the same load capacities. This also means better corrosion resistance will be required though.
I believe the first production aluminum monocoque body was the Jaguar XKE.
Aluminum does corrode, but it was not the cause of the Aloha Airlines incident, flexing of the panels due to pressurizing and depressurizing of the cabin during a lot of short regional flights work hardened the aluminum.
There are alloys of aluminum that are very stiff, T6 comes to mind.
Fiberglass and carbon fiber bodies will not last forever, especially glass-epoxy and carbon-epoxy composites. The epoxy is constantly “curing” to the point that it eventually fails (overcured).
“There are alloys of aluminum that are very stiff, T6 comes to mind.”
T6 is a method of tempering an aluminum alloy and does enhance the strength significantly. The alloy might be 6061, a commonly used, inexpensive alloy with good characteristics besides strength.
You are also correct about aluminum corrosion. While it is easily corroded in both an acidic or basic environment, the oxide is not nearly as badly affected. Aluminum oxide adheres tightly to the base metal, while steel oxide typically does not.
I don’t think the XKE was aluminum. The much later XJ8 was, I think.
The XKE had aluminum PARTS, such as the hood, trunk lid and a few others. The monocoque was welded tubular steel.
I feel cars are made exactly out of the materials they should be. A car made out of rust free material today would be just as archaic later as VW of 35 years ago is today. Why keep a car that’s behind the times so you can be less safe otherwise, burn more fossil fuel and not contribute to the retirement funds of auto workers?