So I took the plunge and tried making a mold of out welding mild steel. I’m using 20 gauge, with one rib in the center, spray foam in the back to keep it rigid and Duratec primer with some gloss additive as the top coat.
Here are some pics
Now my worry is with how long it will last me… what do you guys think? I estimate make 2 dozen parts max. will this set up last? or should i Skim over a tooling gel coat?
If its the polyester primer, it will start peeling, as I the first photo shows.
You could sand it all off, sand back to bare steel and apply an epoxy primer followed by an epoxy gel coat. That should last you hundreds of pulls.
I just started welding another steel mould today. We have found that making them out of laser cut steel is great (and if they stick up you can grind off the welds and disassemble).
We don’t normally bother with painting the steel, we have found that the mould release (19SAM) prevents rusting. When we do paint I start with an etch coat primer (PA10) then Duratech over that. I’ve also had a panel beater paint a mould once while he was doing a car, so the mould ended up yellow but had an awesome finish - cost a box of beer.
+1 with CarbonCactus. epoxy has the bonding adhesion you need to the metal surface.