Rustproofing
Quick question:
What is your opinion about rustproofing the underside of your car here in Montreal? Do you feel it’s necessary or just a waste of money? How about on a new car? If you have any thoughts on the matter, I’d appreciate to hear them.
Chicagoan in Montréal 
I was asking about that too. Is it a scam? People told me that the metal is sturdier under the car than the metal body, which is why the body rusts more quickly. Still I’d be curious as to why one would recommend it.
I think it depends on what you want to do with your car. If you want to sell it in two years to buy another car, I would suggest you do it because it can be a good argument to tell the buyer (if you keep the proofs). Also, it depends on the use you make of it. If you drive a lot, it may be useful. Otherwise, if you use it normally, I would say you don’t need it. The probability is the car will be good for ten years, and even if the parts under the car are not rusted, something will break anyway. And the outside of the car can rust too! My two cents! Happy New Year Frank!
Some rust proofing basics:
1. Your car chassis, the backbone of the car, is entirely stamped steel. Steel will rust in the presence of oxygen or water.
2. Car makers know fact 1. In order to prevent the rust, the oxygen and water has to be kept away from the actual metal. There are two methods of protection: galvanization and paint. Most cars today feature single sided or double sided galvanized steel. This is steel that is coated with zinc. Then the steel is painted. The steel on the bottom of your car, which will be hit more often with small rocks that could remove the paint, is covered again in a thicker flexible paint called undercoating.
The undercoating should be enough to protect the car for a good 10-15 years. Unfortunately, different automakes apply their undercoating with various degrees of success. I suggest either American or European cars for the best protection.
3. Rustproofing is 99% of the time the application of an oil to the steel parts of the car. This oil adds an additional barrier to water and oxygen. In my opinion, applying oil to the bottom of the car will do very little to stop rust from the chassis because it’s going to drip off and be rubbed off, most likely in the same places that the undercoating would rub off.
However, certain rustproofings are applied not just to the underside of the car, but also inside closed sections of metal, such as inside the doors, trunk and into the boxed in sections of metal that form the main structure of the car. This will add more protection as the appearance rust of cars often form in these areas, because the oil can run into places that were not painted or painted poorly during production.
I can recommend Krown rustproofing for this kind of application. I had my car done at Nelson auto repair on Decarie Blvd. near where the new super hospital is being constructed.
The verdict: like other people said, it depends on how long you want to keep your car. If the answer is over five years, I would say it is worth it, as you will only see the results after that period. It may be even more valuable if you drive a Japanese or Korean car that has less factory rust proofing.
Lastly, don’t forget to wash your car and wax it at least two times a year. The waxing is especially important! Wax restores the flexibility in the car paint and prevent chips and scratches that will allow water and oxygen to attack the metal.
As a note: I’m an industrial designer that works at a company specialized in sheet metal work. Also, I’ve restored a car before, so I’ve had the opportunity to see how they are protected from up close.
Thanks everyone. Especially Raymond. I’m familiar with galvanization since we use it in the building industry. Though I wasn’t familiar with what protection was used in the auto industry. Thank you very much for the input. We opted to go with it along with their paint polymer and scotchgarding as a package deal. We picked it up a few hours ago and are very excited about it. It’s our first new car.
Congrats on the new wheels.
Thanks. We are VERY excited about it.
The cause of rust is when the loss of electrons in metal cause oxygen and iron to combine to form what we commonly known to be called “rust” AKA “iron oxide”. The chemical rustproofing treatments work well and usually last around 8-12 months. Some electronic rustproofing methods work very well but a majority probably close to 90% do nothing more than turn on a little LED light to fake it.
The kind of rustproofing you want to stay away from on vehicles is sacrificial rustproofing, commonly used on the underside of sea vessels and underwater pipes. This isn’t any good on cars.
A few of the good electronic rustproofing systems out there use a capacitive system that instead supplies a greater amount of electrons to the car body than the amount lost, therefore making sure that iron and oxygen can not form ‘iron oxide’ even though bar metal is exposed to the elements.
These systems are generally around $500 for a standard car, $800 for 4×4’s up to around $7000 for massive mining equipment.
If you’re in QLD, Australia and need any rustproofing done we use one of the best electronic rustproofing systems. Just Google ‘CouplerTec’ you will see how it works. We also do chemical spraying which lasts around a year and is pretty popular. Proud distributors of CouplerTec, which is a multi-international patented system with a 10 year warranty. So you know you’re not going to get ripped off.
Thanks, Downey Street. I know the general principles of rust since we deal with it in regards to steel reinforcing in concrete parking garages, but I did not know about how the car products deal with it. We have now had the car for 5 years and have yet to have any problems. We opted for the “Diamond Coat” offered by the dealer. Despite not having any problems, I couldn’t say if that was due to the coating or just the factory coatings. Thanks again for the info.