Etch primer then filler or vice versa....?

[drillmaster]

Hi All I'm doing some rust repairs to my van over the winter and my question is when ive welded in a patch and then want to use a skim of filler to blend it in, is it best to prime first and then filler, or filler first then prime? In other words filler onto bare metal or not...?

[ZsZ]

If the metal is fresh then you can use filler (immediately after the metal cleaned/sanded/grinded) othervise clean, weld the patches, clean, etch prime then filler.

[New Kentish Campers]

Hi All I'm doing some rust repairs to my van over the winter and my question is when ive welded in a patch and then want to use a skim of filler to blend it in, is it best to prime first and then filler, or filler first then prime? In other words filler onto bare metal or not...?

My method would be this: Degrease the paintwork on the panels to be worked on. Sand/grind paint back to good metal and leave yourself about 2 inches of good clean metal outside the repair area. Fill and sand it go shape, into the good metal, but never over or up to, paint as you will always be chasing the edge , so as to give a correct shape profile. Etch prime the surrounding metal (etch primer isn't designed to go over filler as its plastic) then apply a primer filler over the entire area, up to the original paint. If you are using 2 pack material, then you could apply your primer filler over the etch primer, wet on wet (obviously allowing the etch to flash off) as both paints chemically dry, its safe enough to do and no need to touch the fresh etch primer, i.e sanding it down before the primer filler. Obviously, use correct PPE with 2 pack paints...

Hope that helps

[drillmaster]

Great thanks for the replies really helpful

[footstuck]

We all use different methods.
This is mine;
Grit blast or scurf of around the area of repair, cut and weld if needed, and dress again.
Then use a 2pack acid-etch over the whole area as a double coat (wet on wet).
You leave the light first coat, till it Starts to go tacky. Then apply a second coat to achieve solid cover. once you are ready for the second coat, apply heat to the area, this helps prevent runs. They will visually reduce with drying, but if they are in an area that needs no filler, they will be time consuming to remove.
The idea is to protect the already thinner damaged areas
The acid etch chemically sets giving an extremely hard as rock base for filling over.
It will not 'Sink as soft primer will.
We used Sigma chemicals. It stopped rust developing for Years without ANY further prep when used in this way. We would pre-blast and etch panels for future repair.
A set of wrought Iron railings which were fabricated and painted in my workshop more than 20yrs ago still shine