Weld-thru primers making sense?

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Just as the title says: do weld-thru primers make sense in lap-welds in automotive repair jobs (fake-spotwelds e.g.) or do these primers give extra trouble(s)?Any types/makes suggested (when the stuff is useful)?Thank you
Reply:I think weld through primers definitely make sense, IIRC they are a zinc rich primer that acts as a cold galvanize process giving additional protection around the spot welds/tacks.NRA LIFE MEMBERUNITWELD 175 AMP 3 IN1 DCMIDSTATES 300 AMP AC MACHINEGOD HELP AMERICA!"Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety.” BENJAMIN FRANKLIN
Reply:https://www.paintdocs.com/docs/webPD...o=075577023240  From everything I've read, it's intended use is protecting steel PRIOR to welding, and doesn't interfere with welding........................but it's not intended to protect the metal after welding.  The HAZ is toast, and requires reprime, if I understand the products.https://www.kent-automotive.com/medi...rsion=78404cb2
Reply:https://autobodysource.com/surface-p...ted%20surfaces.  I guess you remove the stuff after welding.  The zinc stays behind.  So..............I'd hazard a guess it has to be reprimed
Reply:It depends on what you welding.Most welding like Ag and repair just weld over the primer.If for building remove the primer then weld.Dave

Originally Posted by oldwelderman

Just as the title says: do weld-thru primers make sense in lap-welds in automotive repair jobs (fake-spotwelds e.g.) or do these primers give extra trouble(s)?Any types/makes suggested (when the stuff is useful)?Thank you
Reply:Probably like welding galvy I guess.  Never thought that was recommended...........
Reply:

Originally Posted by farmersammm

https://www.paintdocs.com/docs/webPD...o=075577023240  From everything I've read, it's intended use is protecting steel PRIOR to welding, and doesn't interfere with welding........................but it's not intended to protect the metal after welding.  The HAZ is toast, and requires reprime, if I understand the products.https://www.kent-automotive.com/medi...rsion=78404cb2
Reply:I am talking about the following situation:two sheets of carbody metal, to be connected by MIG/MAG welding, using the plug-weld method to mimick spotwelds.when I coat the overlapping part of both sheets with weld-thru primer -to protect against corrosion coming up in the overlap section after the repair-, after that punch holes in the overlap-ara of the top layer (of sheet metal) and position the two part on each other (before the actual plug-welding), looking through the holes I see metal covered with primer.When the weld-thru primer is a sort of zinc-rich primer, this has to be cleaned away locally (welding on zinc is commonly called a no-go (compare to welding galvanised steel), considering health hazards by the zinc-vapoursThat cleaning can be done (by the FITZEE method e.g.) and the individual welds made.Welding not-cleaned stuff here would be equal to welding painted metal, which is generally not advocated in MIG/MAG.But, as there is a heath area in the metal around the actual spot, some burning/evaporation of the primer will happen in the overlap area...., resulting in vapours and sub-optimal corrosion prevention there.Q: are all weld-thru primers zinc-based? In that case I could use the 'normal' zinc-rich primer that is generally available.How does the forum think about these aspects?
Reply:What about a product like steel it? I've used it in the past to weld through and have been very happySent from my SM-A426U using Tapatalk
Reply:

Originally Posted by Slowxj

What about a product like steel it? I've used it in the past to weld through and have been very happySent from my SM-A426U using Tapatalk
Reply:Some weld through primers are copper based I think. Weld though has some wax like properties so once it gets hot it wicks into the cracks to help seal the area. Only to be used on the inside of the pinch weld.So while a cold galv probably wouldn't effect the weld any different then a weld thru, you don't get the actual benefits of the weld thru. I've also been told that there are some products that can be applied AFTER the weld, that are supposed to work similar with less fumes.Airco Auto-Pak 130Forney 235AC/DC
Reply:

Originally Posted by oldwelderman

I am talking about the following situation:two sheets of carbody metal, to be connected by MIG/MAG welding, using the plug-weld method to mimick spotwelds.when I coat the overlapping part of both sheets with weld-thru primer -to protect against corrosion coming up in the overlap section after the repair-, after that punch holes in the overlap-ara of the top layer (of sheet metal) and position the two part on each other (before the actual plug-welding), looking through the holes I see metal covered with primer.When the weld-thru primer is a sort of zinc-rich primer, this has to be cleaned away locally (welding on zinc is commonly called a no-go (compare to welding galvanised steel), considering health hazards by the zinc-vapoursThat cleaning can be done (by the FITZEE method e.g.) and the individual welds made.Welding not-cleaned stuff here would be equal to welding painted metal, which is generally not advocated in MIG/MAG.But, as there is a heath area in the metal around the actual spot, some burning/evaporation of the primer will happen in the overlap area...., resulting in vapours and sub-optimal corrosion prevention there.Q: are all weld-thru primers zinc-based? In that case I could use the 'normal' zinc-rich primer that is generally available.How does the forum think about these aspects?