Underbody treatment- discussion

[m5bb]

I am rebuilding a 72 3.0CS.
It's not a restoration but still pretty authentic looking.

Having discussion with painter about how to do the under body.
His suggestion was to use truck bed liner spray.
He had done this to a number of 60"s and 70's muscle cars.
It doesn't crack or get water under it and is somewhat flexible.
This is not the suspension.
All the suspension has been powder coated.
Just want to protect the metal the best way possible.
I do drive my cars.

What are others doing?

 

[RMP]

Gary,

Mine was scraped completely clean of the original undercoating, luckily no rust or issues, seam sealer put on all joints and seams, then SKS Black Stonguard and anti corrosive compound applied. Looks beautiful.

 

[Honolulu]

I had a '79 6356CSi, euro, 5-speed close ratio, that had been undercoated. Pinholes or stone dings in the undercoating the trapped water against the body, resulting in holes you could put your head through (all this before I got the car for cheap). I sold it. Not really a good car for around town, for me, coming from the 2002 world.

Any undercoat I'd consider would have to adhere extremely tightly to the body metal before I'd risk the above on a car with significantly more value (sorry to any 6er owners).

Maybe POR-15, it's supposed to adhere very well and not allow spreading of rust or separation from the underlying metal. Some don't like it for underbody, it won't look factory, but my hearsay understanding is that it's very tough stuff. No connection here with those peeps... will be interesting to see where this thread goes.

 

[sandhu]

Am thinking having the E9 completely under sealed by a product called dinitrol
In the next few weeks
Before the car goes into winter storage for 5/6 months

 

[E911]

Remember, these cars rust from the inside out typically, not the other way around. Modern etching/epoxy primers and undercoatings applied properly will last several lifetimes on your coupe assuming it now lives a pampered life (no salty/briny winter excursions). The multiple decisions you will have to make while restoring a Coupe are made easier if the default choice is "original". That being said, sometimes you have to work with the local choices you have and their experience/comfort level with products and techniques. In the end, you will probably never have anyone look at the bottom of your coupe again and comment on it's "originality" so unless it's a CSL or some other unique and rare car I wouldn't worry too much about it.

One thing to keep in mind about POR-15... it's a great product for certain applications but it will hide rust like the original undercoating if the metal is rusting from the other side because it has so much structural integrity- the metal can literally be dust and it will hold it's shape over long spans.

 

[mulberryworks]

POR-15 is also not UV stable. It will keep it's gloss when not exposed to sunlight, but will turn matte when it gets a lot of sun. I have a frame section from another car sitting in the sun and it's pretty flat now. This does not seem to harm it's durability, but is a surface effect only. The makers state that POR-15 can be topcoated but suggest should be primed with their stuff first.

CAN I PAINT OVER POR-15 WITH OTHER PAINTS?
Absolutely. POR-15 will accept all paints, including lacquer-based paints. POR-15 Tie-Coat Primer is the best prime coat to use before topcoating POR-15. Be sure to read thoroughly our directions and tip sheets regarding topcoating before using POR-15.

 

[Storage Andy]

I have used POR-15 a lot. My son who is a weekend racer with NASA Mid Atlantic got me hooked on the stuff a while back. It works great. BUt yes you do have to remember the way the cars rust. Read the instructions carefully, test and cover up everything on your body. You do not want that stuff to come into contact with your skin.

 

[Gransin]

I used this water-based 3M product and I'm happy with the result, I used gray on the floors and black in the wheel wells.

 

[wilies13]

In Europe there is Brantho Korrux 3 in 1 available:
http://www.branth-chemie.de/e-home.htm

I paint 2 times.
With 3 times it´s allowed for drilling islands in the ozean.

It has the avantage, that upcoming rust from inside is much earlier visible compared to normal underbody coating.

I am using it in "graphitschwarz". This is close to black like an usual underbody material.
I don´t want to paint it in red (as my car color) due this is not original.

Best Regards;
Willy

 

[Nicad]

You can paint over POR 15 with another topcoat when it is still tacky. I have had great durability on some roof rack parts I made then treated with POR 15 followed by Black trim paint. These parts are exposed to a salty spray all winter. I originally powder coated these parts, but it last one winter before failing.