Underbody restoration - Baffled!

[Spudday]

Hi all!

I currently have my Mazda Eunos on a roll over jig / rotisserie to take the underside of the shell back to bear metal. Its 95% surface rust with a few small sections which had some pin holes which im cutting out & replacing. The surface rust is leaving minimal/no pitting. I've popped in some photos below to show some progress pics - i;m still a little way off getting all the oringial paint/rust back to as clean metal as i can.







Now, where i'm baffled is with what to put on it next. I've tried doing numerous searches online & wanted loads of videos with conflicting information. What do people typically recommend?

So far my findings are...

Buzzweld:
Seems to be popular for off roading land rovers which seems promising. Unfortuntely the rust encapsulator primer they use can be hard for seam sealers to attach to according to the lady at their office when i rang for advice. If i was to go this route i was advised RE primer, then CIO and finish with WAR - the missing piece here is what to do about sealing seams.

Dinatrol:
This one confused me a little - When i spoke to their technical department i was advised to us RC900 on the rustier bits i cant prep perfectly due to some of the hard to reach areas. Then lightly mist the hole underside (which majority is shiny metal at this point with no primer) with the cavity wax (ML) which acts like a adhesion promotor for the final underbody coat of 4941. What confuses me is alot of people swear online with something like a zinc rich or epoxy primer before adding your top coat.

Bilt Hamber:
Their technical department advised from the photos i shared to spray the whole underside with Etchweld & then top with their epoxy mastic. I was then hit with more conflicting information online as people say you must not use mastics underneath of a vehicle as protection as it can be chipped & hold water up against the under side of the vehicle....

Finally alot of forums online that ive looked through seem to agree on the marine Jotun 87 paint as the 2 part epoxy primer that can be brushed on. I'd be happy to go this route if someone can help aadvise what i would then use as my top coat.

What im after is making it as protected as possible as i'm going through all this effort. I'd even go as far as a primer/seam sealer/top coat & some sort of final fluid film/oil over the top if it was beneficial (of course including all the cavity waxes etc for bits that arent shown.

If you've managed to read this far then thank you for your time & sorry for the little story! I'm hoping the PH community can help point me in the right direction or let me know what theyve had good results with in the past!

Many thanks!!

[droopsnoot]

Spudday said:

Bilt Hamber:
Their technical department advised from the photos i shared to spray the whole underside with Etchweld & then top with their epoxy mastic. I was then hit with more conflicting information online as people say you must not use mastics underneath of a vehicle as protection as it can be chipped & hold water up against the under side of the vehicle....

Finally alot of forums online that ive looked through seem to agree on the marine Jotun 87 paint as the 2 part epoxy primer that can be brushed on. I'd be happy to go this route if someone can help aadvise what i would then use as my top coat.

Don't be confused by the name "Epoxy Mastic", it's not like the sort of mastic putty-like substance that you might use to glaze an aluminium greenhouse, it's a 2-part paint. I've used it (or something similar) on the bottom of my project car and it's pretty good, except it stinks while you're applying it. I read at the time that the Jotun Jotamastic paint is the same thing but cheaper.

[remedy]

I'll be corrected if I'm wrong. But, in my mind I would look at it simply. Prime the metal for paint adherence, paint to protect the metal, then add a soft coat because it needs to be protected from stones and road water.

The first 2 are what is done with the metal above the road anyway. So zinc prime then paint.
Then it is an under seal of your choice. Lanoguard, dinotrol, bilt hamber, etc.

[tegwin]

The first step is to get the surfaces clean… like really clean. There’s specific chemicals available for that. Then an acid spray to etch the surface, then get your primer on there. I used por products recently and was pretty impressed.

[paddy1970]

Go with a high-quality epoxy primer like Jotun 87 or Bilt Hamber Etchweld.

Apply seam sealer compatible with the primer.

Finish with a durable top coat such as Bilt Hamber’s epoxy mastic or Dinitrol 4941.

For ongoing protection, use a fluid wax/oil treatment (like Lanoguard or Bilt Hamber Dynax) as a final layer that can be refreshed periodically.

[Belle427]

Im no expert but Jotun suggest it can be left as a topcoat so you could just go over it with something like Bilt Hamber UB.

[Jbliss]

I did exactly this job

Once everything was ready to go I had the car 2K epoxy primed, I then seam sealed and went over the top with Raptor Bedliner which is great. I then went to town with the cavity wax and any additional underbody protection you like, although it's not really needed.

Edited by Jbliss on Tuesday 17th September 15:47

Edited by Jbliss on Tuesday 17th September 15:49