Painting Under Sills - What With?

[JonnyAlpha]

Hi;

I am repairing the Under Sills and fitting new Sills on my Mini. Looking at a few other projects guys / girls seem to completely paint the inner sills and inside of the outer sills before welding on?

I was going to paint the Inner Sills and underside with Expoxy Primer (Jotun Jotamastic 87) and leave it at that and then weld the Sills On. My other plane was to leave the areas that will be welded bare metal and treat with U-POL Weld Through Primer, but not sure how they will react where the U-POL meets the Epoxy, or should I just cover with Epoxy Primer?

Most Primers are not waterproof and need a top coat, but Epoxy is different right? So do I need to apply a Top Coat to the Primer under the Sills where it cannot be seen?

The remainder of the underside will be treated with U-POL Gravitex Stone Chip over the Epoxy Primer could I use that under / between the sills (Applied with a brush or a standard gun so it goes on smooth or should I Shutz it the same as the rest?

Sorry if I sound a bit thick but never done this before and after all my hard work cutting, de-rusting, fabricating and welding it would seem pointless to mess up the painting :-(

Thanks

 

[richie00boy]

Epoxy primer is not resistant to UV, but everything else it is. So inside sills it doesn't need to be topcoated.

Just remove the coating where the weld is to be. Then after welding spray (thinned) epoxy primer in the sill using the same method that you would cavity wax, i.e. one of those 360 spray head tubes. No need for cavity wax then.

 

[steveo3002]

if i was doing it epoxy primer where it wont get burnt , mask off a inch or so where the welds need to be a use weld through primer

after welding i would use cavity wax to drown the seams and epoxy with stonechip on top outside

 

[MG David]

I have used the method indicated by steveo3002 although I have sprayed light oil, duck oil, in before the cavity wax. This is in the hope that the oil will soak into the seam at the bottom between the spot welds more than the cavity wax does.