Underfloor Product Compatibility

[Poobah]

Evening all, I'm currently doing an underfloor resto on my car and following bare metalling it all I'm thinking of using Dinitrol RC900, then Jotamastic 90 primer, 3M 08800 Sprayable sealer, then an iso-free colour over the top (something like Ultrimax 2 or similar).

Obviously I need to do a test panel to be sure, but can anyone see a fundamental issue of product compatibility with that process?

 

[Poobah]

Can any provide any feedback on this? Thanks in advance.

 

[marlinspike]

Is this underneath the car? Or the floorpan from the inside? The RC900 is a rust converter ... I have only used Hydrate 80 on my resto but it really needs to be used as last resort if you can't get pitted rust out.

Haven't used the Jot90 but it's very highly regarded on here so should be fine. The 3M seam sealer is what @Jim881 used on his car I think. I thought it looked a nicer finish than the Gravitex I used on my wheelarches.

I can't see any issues with your choices. I'd only warn that any untreated rust will get worse or come back if not dealt with properly, as I am currently finding out myself.

 

[Poobah]

Underside.

The RC900 is more to neutralise the surface before I apply anything. The entire underside is back to bare metal, but with the best will in the world you'll never get every single tiny spec of crevice corrosion out from between seams within pits etc so using something to converter anything small seems a sensible approach. The RC900 is also helping as taking the entire underside back to bare metal is not the work of a moment (as I'm sure you've experienced) so I've been able to do a section, neutralise it with RC900, and then move onto the next section a few days later. It's avoided any risk of flash corrosion on sections I've already done whilst I get this mammoth job completed.

My main concern was whether I'd likely see any compatibility issues between the RC900 and the Jotun, or between the Jotun and the 3M.

 

[barracuda816]

According to Dintrol the RC900 should be fine as it basically sets as an epoxy resin. I have not used it but am really interested to see any test pieces. It's difficult to remove every single last trace of rust on older (poorer condition) cars so anything that helps slow down the inevitable return of the Red Devil is a huge bonus.

 

[Poobah]

I think the problem is, even when you've bare metalled something, there will always be some pitted corrosion cells that you can't see but remain. That's evident on mine where it's been all the way back to bare metal with a bristle blaster but as you can see here the surface in some areas has turned purple after applying RC900 which implies it's converted some corrosion in those areas.
Using the RC900 (or something similar) gives me a bit of confidence that I've done as much as I can to deal with those pitted corrosion cells.