Underbody Coating for Winter
 

Hey guys, just purchased a car and I have noticed that the under-body coating was starting to fade. I was wondering if anyone knew any good shops that provided under-body coating that is of quality work.

Also, I was wondering if there were shops that would take under-body coating products you provide for them. I have read a lot of positive reviews on por15, and it would be nice if a shop would use the product I recommend rather than their typical coatings.

Information on the the price of a typical under-body coating job would be nice.

As someone who spent a few years restoring cars (Mainly old Mercedes and Porsche) undercoating SEEMS like a good idea but it its not done at the factory as soon as the car is finished you are sealing in dirt and moisture that will cause more problems than its worth.

In theory its a great idea as it is designed to seal the underside of the car from the damages of sale and dirt. It does do this for the most part but where it fails is that it is done on a car that is not clean. No mater how hard you try, if its not done at the factory, it will have dirt and moisture on the underside of the car. When you seal that in there you basicly make a sand paper like material. When that has a few years to rub through the surface on the underside of the car and the sealed in moisture eats away at the metal you get rust. Most people will not notice it because you cant see it but its there.

I used to think it was a great idea until working on cars with undercoating and seeing what happens to the car after years of having it on I have changed to simply washing the underside of the car every month or two with a good pressure washer and a foam lance to get some cleaning power under there.

someone correct me if i am wrong but isn't por15 a rust converter/primer and not undercoat?

i don't know what car you have bought, and you did not post pics of what it looks like under your car... but my friend bought a jdm silvia and the underbody has a lot of surface rust around anything welded and some surface spots where the car had bottomed out on something (car is lowered on coilovers). he used a wire wheel to clean up the rust, covered it all with por15, and then undercoated the areas with a crappy tire rattle can of undercoat. it's been 3 winters for him now and his repair work is still good (albeit patchy because he did not undercoat the entire underbody).

otherwise... this has been covered before. you need to do a search (and maybe keep a flamesuit handy because the discussions sometimes get heated). personally i don't care much for aftermarket undercoat add-ons some dealers do because of sloppy application (overspray on body and exhaust, drain holes end up getting plugged), and it can add a lot of unwanted weight if you are into that sort of thing (ie. pick up a can of paint and you'll understand).

Por15 is a good product for sure. Its not undercoating but a rust converter and it works well. I would be far more likely to use this than a true undercoating on my car.

yeah i wasn't sure. a painter once told me that you can't just use por15 without covering over it with something because left exposed it will break down and it will start rusting again.

POR15 is your best bet. It's just very time consuming to apply. I had my 4Runner undercoated the typical spray on way and it's OK but if I had the time and patience I would go the POR15 route.

Read a post elsewhere, where someone hit the por15 coating with a rock and it didn't chip, which was why I wanted to coat the underbody with it unless he was exaggerating.

The cars a 1992 NA miata, hopefully there are shops that know how to apply por15 because I've read that there's a lot of steps and drying processes to coating metal with por15.

You seem very fixated on Por15, i know it's good for what it is designed for, but i believe that designation isn't undercoating... Supposed to be for painting frames etc of restos...

hm... i was just looking at their website (it's been over a decade since i last used this stuff)...

what dared3vil0 might be talking about is this: TOP COAT

what you are thinking about might be this: http://www.por15.com/RUBBERIZED-UNDER-COATING_p_57.html

:suspicious:

Didn't realize they made more than just the top coat, which you are correct is what I was talking about.

me too. i had no idea they had so many products now. back in the day it was just the por15 rust converter and that was it... so in answer to your question OP: i guess it can be done then.

just a followup...

I have a lot of experience with POR-15. It is not a "Spray on the bottom of your car" undercoating. POR-15 is only good when used with seasoned metal. It would be ideal for things like sub-frames, suspension arms and other suspension components on your miata. Unless you're planning on pulling all the factory undercoat and paint off the body, it is not a good choice for simply painting over what is there.

POR-15 is NOT GOOD on new metal. If you have any new steel, even with the proper etch and clean steps it's not likely to hold. When properly applied to used metal (metal that has had some rust or oxidizing of the top surface), its essentially bullet-proof.

-DAve

Your standard fare rubberized undercoating in a can is just as good, but before you undercoat anything on a car, you have to completely clean and degrease the underside with a stiff brush and some heavy duty cleaner. Any rust spots have to be treated before you apply to that location. I did the wheel wells on my Subaru and it turned out great, but I also spent a lot of time with the wheels off doing a major cleanup in order to ensure I wasn't actually making the situation worse.


Por-15 in it's standard form is NOT supposed to be used as undercoating, it's meant to stop rust on rusty metal and be top coated if it's exposed to UV rays.