In my case, no previous experience working with MSS, so I kept it at least 1/2" to 3/4" away from where I would be welding. In those areas surrounding the plug weld holes and on the flanges to be welded to the floor, I applied EuroSpray Weld Thru Primer Copper.Speaking of MSS and welding... I'm going to be using this on frame rails, etc. But I've been wondering if you can use it on the backside of where I'll be spot welding (i.e. bottom of the frame rail flange where I'd be spot welding the new trunk floor from the top). Or should one just leave the MSS back a couple of inches until welding is done and then coat backsides? Sorry for a possibly silly question. I'm new to all of this and just trying to learn and prep and plan ahead. Also Boss5Oh, what copper-infused weld-thru primer did you use and did you like it? TIA
We only have one automotive paint store in Prescott, Wesco, and I used what they had. Not cheap, about $38 a 15.2 oz can. Another guy 7T0S here on VMF has been using Cobre WTP, but I could not even find a dealer for it. The EuroSpray product seemed to work OK, but nothing to compare it to. In the area where I did the plug welding, I got some spitting initially but that settled down as I worked around the plug weld hole. I even tried scratching though the WTP to see if the weld started up better, but no help and maybe not as good.
MSS suggests two coats which I did. It goes on pretty thick with a brush, so there could be a lot of material to burn off. I would be concerned about the fumes generated if you apply it near where you plan to weld. The material data sheets that come with the MSS warn about using a respirator when spraying the product so it has some harmful ingredients when airborne. When applying it with a brush, it has a very potent odor. I kept the garage open when applying it and boy did it stink up the place by morning.
I hope this helps, but difficult for a newbee to help another newbee.