Underbody coating ?

[B1N9S]

I am in the process of sorting out the underside of my 02 project and am doing a few weld repairs, before moving onto the coating.

I have a plan, but can someone confirm I am doing it correctly ?

My plan is as follows:

1). Carry out repairs (obviously)
2). Clean area as best I can and treat any surface rust with Dinitrol RC900.
3). Epoxy Primer the whole underside using Lechlars Epoxy Primer (How many coats ??)
4). Seam seal joints and welds. ?
5). Cover primer with Dinitrol underseal or other (again - How many coats ?)

Have I missed out anything, or would you do it differently ? I am torn between using the Dinitrol underseal, or changing to using UPOL Raptor (truck bed liner).

A couple of things that are bugging me. The car has had bit of welding on the floorpans. Should I cover the welds with seam sealer before I add the underseal ? And lastly, should you actually seam seal the car underneath ? Or should it just be sealed INSIDE the cab ?

Hope all that makes sense ?

 

[rikrobson]

OK,

I'd do it 2,1,4,3,5

clean, weld, seal, prime, coat

if you weld first then clean you'll probably fine some more work to do.

if you are worried about the floor pans the re do them. otherwise seal and coat.

 

[B1N9S]

Sorry mate. Yes I have cleaned the whole area first. But by 'clean' I meant to prep for paint 'clean' !!

I'm not worried about the floor pans, but would you put seam sealer over the welds ?

 

[anjum]

I always put the epoxy primer on first before the seam sealer as seam sealer will fail before the epoxy primer and can trap water under it. I normally put another coat of epoxy primer on the seam sealer just to be safe.
As for the welds treat them as the rest. There's brush-able seam sealer as well. Use the polyurethane seam sealer.

 

[MG David]

For me it would be 2 coats of epoxy. Then seam seal. Then a 3rd coat of epoxy.
Also I normally try to remove surface rust rather than treat it. Although once surface rust is removed I go over with a weak phosphoric acid solution as an anti flash.

 

[rikrobson]

In theory the seam sealer should be encapsulated by the epoxy and coating, but belt and braces is good if it means not having to do the jub again in the future.

there shouldn'd be a nead to seam seal the welds if they are continuous buy if there are gaps i'd seal them all.

Yes make sure the metal is "clean" before applying anything. make sure also that there is no rust as the tin worms will wake. the treatment only realy deal with surface rust. if is like sanspapre then remove as much as possible mechanically prior to paint

 

[B1N9S]

Cheers guys. As always, great advice on this forum. I now know what I need to do to proceed.

 

[B1N9S]

So. I finally got round to starting this.

So far, I have cleaned off the old horrible oily mess. And I bought some Epoxy Mastic 121 and have covered all the welds and any vulnerable areas. (bleedin expensive stuff). So, my plan now is 2 coats of Epoxy Primer. Then sealer (to be sure, to be sure !), then a last coat of epoxy primer. Does that sound like a decent enough plan ?

A couple of pics.

 

[RaceDiagnostics]

Did you think about using over paintable under seal?

 

[norsa]

raptor is quite impressive. 2k stonechip essentially
Nick^^

 

[123hotchef]

yeh raptor bed liner is great stuff

 

[Bobo]

Can the Raptor be overcoated with normal 2K aswell? It's gives a stonechip crinkle type finish too doesn't it?

 

[Bobo]

raptor is quite impressive. 2k stonechip essentially
Nick^^

Silly ****, fancy not noticing that bit...

 

[norsa]

Not silly **** at all. I'm saying its a 2k product but can be overcoated with 2k. The finish can be varied depending on whether you use a conversational or schutz gun. I used some recently and reported. See' Mr Midge' in projects /automotive and bikes

 

[langy]

Clean metal then 2-3 coats Lechlar epoxy, then Graitex or Raptor, raptor is preferred

 

[keithski122]

Why would you want to overcoat raptor when you can tint it to what colour you want?

 

[B1N9S]

Thanks for the replies. Raptor it is then.

Anyone want to buy some Dinitrol underseal !

Langy, when you say 'clean metal' are we talking shiny clean ?

Cheers.

 

[123hotchef]

is the raptor underseal the same as the bed liner

 

[norsa]

Its exactly the same stuff.
When Langy says clean metal he is indeed talking shiny. That's all he deals with.

 

[Swift&Bold]

Jotun is a good and cheaper alternative to 121.