undercoating question

...........FWIW.........Many automobile manufacturers have gone away from external undercoatings because they eventually trap moisture between the undercoating and the metal which cause big time rust problems...eventually. It's done internally now in regard to sound dampening and the typical finish underneath the car is a hard 2-part epoxy or poly-urethane type sealing paint that is not much thicker than the paint used on the rest of the body. I do wonder whether they're using some kind of plastisizing component in the chassis paint that makes it more chip resistant. My wife's Maxima and my Lexus both have no traditional style undercoating underneath them and they're still rust free after several years here in upstate NY where tons of salt gets dumped on the roads every winter.

Thanks, Tim I did not know that they moved away from undercoatings. Is that expoxy or poly sealing paint specific to undersides of cars? What brand would you recommend? It sprays on with just a regular hvlp setup?

Took the original paint off the floor panel (looked thin and didn't trust it) and sealed it with POR15 - that sure makes a nice hard finish. Would like to put a protective coat (besides POR) on the frame so I can store it wrapped in tarp/duct tape. I will be working on the body over this winter.

Right now, it is still pretty easy to paint the underside of the frame since it just tips over - so think I'd like to do that next.

Remco

.............Just go to an auto paint supply store that deals with the dealerships and paint & body shops. They'll know exactly what the shops are using and maybe even point you toward whatever's best for the DIY guy. I've been using Zero-Rust for a few things like suspension parts with good results. It's a high-solids alkyd enamel, I think, that brushes on easily and won't do a number on your lungs like POR15 can do if you don't have good ventilation. It's also less sensitive to temperature and humidity conditions since it dries slowly by evaporation rather than hardening quickly when exposed to moisture/humidity the way that POR15 does. I actually screwed up while using POR15 several years ago with inadequate ventilation and it caused a big respiratory problem for me. I'm OK now but still have a residual hyper-sensitivity to POR15 fumes.

Thanks - I'll do that over the next couple of days.

Yeah, POR15 stinks /bad/. I also can't take smells like that long as they tend to give me bad headaches (my daughter's nail polish remover has me leaving the house for a while) I had my garage door open while brushing it on but thanks for the reminder.

Another product you can check out is one from england called Waxoyl. It's a product that comes with it's own applicator and you simply remove all the plugs from all the holes in the structure of the body (if you have any plugs alot of cars don't) and spray it throughout the cavities that make up the frame of your car. It works a treat and is reasonably non-toxic. Unfortunately however it is kind of expensive.

Sorry, It's not from england it's from switzerland..... Read a good english car mag called practical classics all the time and I thought it was english duh. Website:

I've used Zero Rust and I've used Por-15 and I think both are good products. I have only once used Por-15 to any great extent and when I did it I did it in the garage with all the doors and windows open plus I had a couple big fans so I have very good ventilation. What amazes me is that I have read that some people are more prone to having issues with the Por-15 funes. Honestly, I just used the regular black stuff and I couldn't believe what I thought to be a lack of smell. I was expecting this nasty stuff but realistically it wasn't a big deal. But I can appreciate that it's bad stuff that you don't want to be in constant contact with.

Fluid Film. This stuff reamins a liquid and

recovering areas.

Thanks for all the good advice, guys. I'll check them all out.

Remco

I also don't like undercoating. The chassis of my beetle was never painted and lived outside of a garage day and night for 22 years. The only treatment was paraffin. I have seen undercoating beetles completed rust out.

Joao

My sister used to live in central Michigan, and the roads were oiled gravel. There, if you did not have some sort of rubberized undercoating the gravel would wear away nearly anything all too quickly.

............As I mentioned earlier, the modern paint formulas for the undersides of a vehicle must have some kind of formulation that makes them chip resistant in comparison the conventional paint that's used on the body panels. Thick undercoatings have been proven to cause more long term rust problems than what they prevent in the short run. That gravel flying around underneath the cars in central Michigan will eventually cause cracks and/or pulverized areas where moisture can penetrate an undercoating. That's when the undercoating starts working in reverse......keeping that water trapped against the metal and creating rust that corrodes even faster than if the area was open to the air.