Howdy HAMB! My 54 truck cab had a soggy floor so I framed out a new one with 1” .120 wall square tube. I made paper templates and cut most of the floor out of two big pieces of 16g that’s all bead rolled on the flats and drilled every 3” so I can rosette weld it to the framing. I need to paint the framing while I still have good access, and the bottom of the sheetmetal too. My question is what’s the best way to keep rust from forming between the floor and frame? Some paint will burn off in the welding and it’ll be hard to clean thru the 3/8” holes to super clean metal before welding. I’m thinking seam sealer might just permanently trap moisture because water loves to crawl into tight places. What’s the best way for a guy in his driveway to do this? Or am I over thinking it?
Might try to cover the metal with this, and then seam seal around welded areas. https://www.amazon.com/SEM-39783-Weld-Thru-Primer-oz/dp/B00063ZPBU
Ok cool so I’ll paint it up then clean the top surface and paint that with the weld thru, then probably undercoat later at my buddy’s with a two post lift.
1 Weld-thru primer 2 Seam sealer 3 Paint 4 Undercoating In that order. If you seal the seam, how is moisture going to get in? It isn't, unless the seam is not sealed.
One thing to consider.....the weld thru primer is supposed to be the only thing on the metal you are going to weld. You could paint the underside of the floor and the tops of the framing, but I'd think you would need to mark where each spot weld will be, use a spot weld cutter bit to remove the paint in that spot, shoot the spot with weld thru primer, them assemble and weld......THEN do all the rest of the sealing steps. If you don't remove the paint at the spot weld, you likely will have difficulty striking an arc for the weld. Another approach would be to use body panel adhesive to attach the floor to the framing with an occasional spot weld if it is really needed at some points and/or makes you feel better. If using the adhesive, glue it on and seal and paint as indicated. The adhesive will act as sealer of the floor/framing joint as well or better than anything else.
Well I’m building outside in my driveway so I really need to keep the cancer at bay and it is hard to paint well from underneath. My plan is to clean the metal frame, paint it really well, then sand off the tops of the rails to nice clean metal and spray the tops with the weld-thru. The sheetmetal I’ll do the same- paint it, then sand a margin around each hole and hit with the weld-thru. The 3/8” rosette welds are going thru 16g into 1/8” steel so with a mig the amount of heat I gotta put into the metal should be minimal- hopefully most of the paint will stay on there until I can do a good cleaning and seal up from underneath. Thanks all for the helpful and kind posts
I'd really recommend you use a spot weld cutter bit in your hand drill to just remove the paint at point of the spot weld....do not sand the tops of the framing to bare metal. With the floor clamped into place, a simple touch of the cutter bit will have bare metal in no time. Under that scenario, where you are painting first, I don't think weld thru primer is even necessary. After welding, follow with seam sealer and maybe another paint coat along the seamed area. A good rubberized spray undercoat would also be effective, imo.
Purely by accident I found this out?? If the Epoxy primer is still wet it welds like it's not there. Brush the floor pan, brush the frame weld it with wet paint. This doesn't work if you're slow and the primer dries. Then you get a epoxy primer sandwich. Finish off with seam sealer and nice primer/paint. The Accident went like this -- I turned around and some shit got painted with epoxy primer while I wasn't looking. "WTF!! I gotta weld that and I need to do it now". Then I welded it and it was really nice. Tiny bit stinky but nice
I’m with big duece. U-POl weld thru primer. Get the copper, zinc doesn’t weld as nice. I use it daily in the body shop. Sent from my iPhone using The H.A.M.B. mobile app
I painted the pan bottoms and the floor frame, cleaned the paint around the welds, hit the bare metal with weld-thru, installed the floor pans and welded it all in solid. It’ll get seam sealer later but for now peace of mind is a good thing!
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