Hey Stocker...since you're working in this industry I have a question on the side for you.

Back then my mechanic jacked up my car on the side sill using a floor jack, which to my surprise the sheetmetal bended and some of the paint came off. I'm just wondering if it's ok to just apply touchup paint to the damaged area then seal it with some rubberized undercoat? Or is the galvanize coating already damaged?

 

Untrue. A single counterexample invalidates a generalization. You claim that cars will rust after 6 years if not treated. Likewise, if I claimed that first generation Mazda Proteges do not rust then a single counterexample of a rusty Pro would invalidate my claim. .

If you want to test a null hypothesis that first generation Mazdas are not prone to rusting then considerable further evidence woudl need to be gathered and you would need a farily large sample to reject that null hypothesis. That is probably not worth doing unless you work for Mazda.

Some evidence on the susceptibility of first generation Mazdas to rust can be gleaned from searching through the first generation page on this board. You will find problems with front axles amd wheel bearings and numerous electrical problems, but you will be hard pressed to find anybody complaining that his car is rusting. You will also find plenty of pictures of first generation Proteges that are in very good shape despite being in Northern climates. I don't believe mine is the only one. Similarly, if you go to the Miata board, you will find few, if any, complaints about rust and plenty of really nice old Miatas.

Althuogh my comment about my car was made in response to your blanket claim about cars rusting, I am willing to concede that some cars are still susceptible to rust if the metal is not properly galvanized. A 95 or 96 Prelude could be an example of such a car.
It is also possible that third genration Proteges are also prone to rust. We will find out in another three years or so.

However, I am still dubious about whether rustproofing will do any good on a car that is prone to rust. If, as you claim, newer Proteges are not made with metal that is properly galvanized and are prone to rust, I would not buy a new Protege for that reason alone. An aftermarket rustproofing job will not make up for lack of galvanizing. Any car prone to rust should be avoided. In terms of cost and trouble, chronic rust is much worse than an unreliable engine or transmission. Ask anyone who had a BMW 2002 or Porsche 914. A ring and valve job or a new transmission is small change compared to a floor pan.

I will admit that I am perhaps generalizing too much about aftermarket rustproofing due to my own bad experience with cars that were rustproofed, started to rust in three years and then suffered from perforation after five or six. It is possible that newer aftermarket products will not clog drain holes and cause rusting, as was the case previously. As long as you are convinced that it does no harm then the worst is that you waste a few hundred dollars.

In the meantime, I am going to check with my neighbor who owns a car dealership about why aftermarket rustproofing companies have disappeared. There is not a single listing in the Central New Jersey telephone book. The Philadelphia telephone book has a single listing for Ziebart with a small yellow pages ad that mostly touts stereo installation and aftermarket accessories. Years ago there were Ziebart and Rusty Jones ads on TV all the time. I can't remember seeing one for more than 10 years now. What happened to these companies?

 

My 91 is in pretty good shape, no damages at all. It's has been rustproofed twise and still there some rust in the bottom of the car. I've owned it only for 2 years now. That's where cars usually start to rust. Newer Pros as well as new Mazda6 have no rust proofing done in in the bottom behind rear axle.

 

Its perfectly ok to touch it up. galv coatings are what are refered to as anodic protective coatings. Meaning the galv will rust preferentially to the steel. As long as you don't have long wide continuous scrapes in the coating you are ok. Panels start rusting once the area loses the coating in about an area the size of a dime.
Stocker.

 

Dude, you can spout all the garbage you want out of your 1st year statistics text book. This has nothing to do with turning your observations into a stats question. I was just making a point. Of course you can find Pros that rust in 3 years 10 years, etc that is the nature of a normal distribution. What I am saying is most pros will start to rust after 5 years. I know this from my line of work, and from that fact that Mazda gives a 5 year rust warrenty.
Christ, everyone with a text book these days thinks they are an expert statician.
Stocker.