Good video and great topic for discussion. Weld though primer is essential if you cannot access the area after the welding, like a patch panel or rocker. Welds will start rusting immediately. Weld through primer melts and leaves an etch behind to protect the weld. Also, using things like epoxy that are not meant to be welded before welding contaminates the weld. That is why you epoxy weld was so pouros.

Had it not been for you I would have never knew this. Thanks so much!

Thanks for taking the time to do this . We will all learn from it :)

Looking forward to seeing your results

Interesting video. Looking forward to the results. Thanks.

Nice T shirt! You got it going on in your shop. Always something to work on.

Enjoy your videos. My thinking is that weld thru primer works best where two panels are sandwiched together like plug welds or pinch welds forming a barrier around the welds that are between the two sheet metals sandwiched together as in your experiment in the last part of this video. I also believe the same about scraping plug weld holes clean prior to welding for a better weld and would not lose weld thru protection. I have considered doing the same experiment. Nice to see you doing it. Looking forward to seeing your results.

Will be a good test. I did a similar test awhile back, it held up good with the weld thru. I didn't video any of it. I have never used the 3m and I know everyone has their favorites. I have had good luck with the Medallion rs512.

Can't wait to see how this comes out

I use the weld thru and I go back and forth between scraping it out of plug welds. Been reading a lot on the SPI forum and they suggested after welding to tape up seams and flood with epoxy. Either using a 360 wand or the like to get the cavity covered. I use the cavity wax after painting with good results but I also don't have any repairs over 6-7 years old yet. But the vehicles are driven in salt so I would think it might be a fair test

Interesting - can't wait for the out come.

Defiantly will be interesting to see how this turns out. Though outside of the weld through primer, wish I could weld half as good as you. I gave up on it, while my welds held up and penetrated, no matter the settings or things Ive tried, they just looks like someone blew their nose on it lol

Very interesting experiment. Will be looking forward to seeing what the outcome is.

THANK YOU...for sharing. Nice test.

Cool. Funny, I just bought some weld thru primer on my way home from work tonight....

Should be a good test. Looking forward to the findings.

I wonder if all weld thru primer is basically the same or if some is better than others. Great video Roger. Looking forward to this. If it sucks, I will not sleep at night with my 1953 truck!

Thats interesting! Sorry, new subscriber here. Nice to meet you! I'm curious to know if the weld will rust or not.

Must have been my problem on my rocker replacement project a couple years ago. i used weld through primer and welded over it, could never get a good clean weld, always popped real bad with a rough bubbly finish. i blamed it on sheetmetal impuritys from cheap parts. rockers for my truck were only like $20-$30 each. never thought a product called weld through would make the welds so horrible.

it's funny because everyone hates weld thru but almost no one understands how its supposed to be used. As far as I understand when used in a weld like a plug weld, the primer melts into the puddle as you weld and adds corrosion protection to the weld itself. Not the surrounding metal around the weld. You see people using it, and then scraping it out of the hole before they weld, which totally defeats the purpose. But then again like you, I am usually wrong about everything... But it is called weld thru primer, and not put around or behind your weld primer.. lol

Great video Roger. I was thinking as I was watching it, why don't you cut out the section on the Camaro rocker? That is a good science experiment right there. See what (if any) primer they put in there and see if it has rusted.

I've read that weld thru primer melts into the puddle of the weld and provides corrosion resistance in the bead as it re-solidifies. I don't scrape the weld-thru primer away on my plug welds anymore. It will be an interesting experiment to see the results I myself started using it regularly. Have you considered the structural integrity of a section repair on the rocker of a unibody car? Just a question I over analyze everything.

I’d just like to mention that weld thru products aren’t meant for direct exposure to the elements. They’re intended to be used in a protected environment. That means inside a panel. They don’t explain that very well, so I’m not surprised people don’t understand that. So sure, it will rust outside. Really, it’s a light layer of protection. Usually the parts are spray painted later. Interesting results though. In addition, it’s expected to be used, not with regular welding, but with a spot welder. By the way don’t weld through epoxy, serious gasses are produced. Not good. Not immediately as dangerous as welding in zinc, but close enough.

I think you should try sem copperweld, I've had very good luck with it

Is weld through seam sealer better for overlap welding?

think the two welds will rust the same? on the back side

How did this test work out on this. I couldn't find an update video on it, but I am in a similar dilemma on how I can treat the inside of a frame that I am welding up.

Hi did it protect the underside of the test panel? I didn't see the after video for that.

That pneumatic tool that you used to punch the holes in the sheet metal flange: What is it called?

Is there are result video? How about adding a link to the description! Thanks

So, is there a "RESULT VIDEO" from this test anywheres....?

Why scrape weld through primer off before welding?

I don`t understand why it should rust because of moisture when you welded and painted your peace and put it outside. Teach me. You locked it

Not all weld-thru primer is created equal. Check-out a product by Medallion, it's a etch-weld primer RS-512. I'm still watching your videos & still find them educational. Did you ever check-out the Dustless Sand Blasting.

That weld thru primer sucks! Still loving the great test videos.

I have to do the same damned thing with weld through primer. stuff is great... but like ya said. it a bitch to actually hit directly over.

Isn’t that what seam sealer is for?

3M has a good video on you tube on weld thru primer . they explain its purpose and how to use it.

straight argon might help with welding splatter

Somebody get this guy some panel bond

so ........ no conclusion then ?

Can you do my Mustang

the video and the comments.... sooooooo many wrong ASSUMPTIONS. and I'm ok with that, BUT when people act like they are right about their guess and everyone else is wrong... shame.

Weld thru Primer: Quote: "I hate the stuff." Now, you are going to do a test of a product. Note: Do everybody a favor go back to 3rd grade and complain to your teacher that you stopped learning at the end of the 3rd grade.

too long