Weld through primer

[65 drop top]

I removed the spare tire well on my '55 Chevy and am about to plug weld in a flat panel. I want to protect between the flange and panel from rust. I started to spray it with a galvanized weld through primer and started thinking if that is the right move or not. Is the galvanized weld through primer best for corrosion resistance? When plug welding, can you actually weld directly to the primer or do I need to hit bare metal? Using a mig if that makes any difference.

[dhutton]

I have had good luck with 3M weld thru primer. It allows welding without removing it to bare metal. Some guys use epoxy but as near as I can tell it just burns up and you have to remove it to weld.

Don

[Wall]

I have used the SEM weld thru primer and a few others that worked but were really a pain to weld with. Even if you did clean the primer off just at the plug weld hole it still splattered and sounded like bacon frying.

The brand that I have heard works really well is Medallion RS 512. http://www.medallionrefinish.com/Editor/assets/tds/rs-512_tech.pdf

I haven't tried it yet but plan to next time I have to use weld thru primer.

[blu72nova]

I've used zinc and copper based weld through primer. I've had better luck with the copper as far as ease of welding. In either case, you can tell you are not welding to bare metal. Remember it's still important to seam seal even with weld through primer. Here is what i use.

https://www.amazon.com/SEM-40783-Copperweld-Weld-Thru-Primer/dp/B003TQGT4S

[MuscleRodz]

I have used them all and prefer upol over 3m and sem

[mikey]

Upol is the way to go��

[Buryingthesun]

I use SEM copper weld. I always mask the areas I'm welding, surface blast to remove paint or impurities. Then while its still masked I spray the SEM copper weld on.

[badazz81z28]

Do you have a part # for the Upol?