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05-28-2018, 01:07 AM | #1 |
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Applying weld-thru primer
Can I get a quick walk through on the correct way this stuff gets applied...
I bought a can from o Reilly's S.E.M. I believe was the brand name. I applied it as the directions said. Seemed to be pretty good. I needed a lot more and was tired of them only having one can in stock so I went to an actaul automotive supply store and purchased the stuff they carried. Can't remember the name of it it was $30 a can though. I began reading the directions on this can before I used it and it states "not intended as a primer". What does this mean?? My process to applying weld-thru is to completely remove all the paint down to bare metal where ever the metal will be sandwhiched together. I then apply the weld-thru to completely cover all the bare metal. Now I'm second guessing myself and think I should be applying a regular primer as well. If I do should I be covering all the bare metal with a regular primer and then shooting some weld-thru primer wherever I'm welding? Can you guys walk me through how you use this stuff?? Thanks. As a side note I am wearing a respirator whenever welding over top of the weld-thru primer. |
05-28-2018, 07:00 AM | #2 |
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Re: Applying weld-thru primer
ive been using the 3m weldthru ...got it from oreillys ...and it is close to 30 a can....but you don't want regular primer where you are welding...itll burn when you weld it defeating the purpose of the weldthru and make your welds look like crap....
I spray the weldthru directly on bare metal...let dry...then weld I may not be doing it right but that's the way I do it
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05-28-2018, 08:19 AM | #3 | |
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Re: Applying weld-thru primer
Quote:
A lap weld is avoided whenever possible to alleviate any corrosion concerns. This is why a butt weld is preferable, but not always possible or desired... as other readers may appreciate knowing. As a side note to your side note, a respirator should be worn at all times regardless of what and when you are welding with or without weld thru primer. (maybe this is what you meant?)
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05-28-2018, 10:47 AM | #4 | |
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Re: Applying weld-thru primer
Quote:
Zinc, think about that, weld through primer is 90 something % ZINC! You want protection! 3m makes a cheap disposable welding respirator. https://www.3m.com/3M/en_US/company-...4776422&rt=rud And when you apply it, do so ONLY where your panels will be overlapped. here is a photo of when I put the gutters back on my cab. I masked off just where the gutter goes, once the gutter was installed you could see almost zero of that weld primer. It's not a good "primer" under your paint or other primers, it doesn't adhere even close to automotive grade primers that you will be using on the rest of the truck. It's designed for between overlapping metal. Another couple of tips when using weld thru. DON'T APPLY IT TOO THICK! And wait until it is FULLY flashed before welding. If you have too much or it's not fully flashed, your welding will be one hell of a mess. Post the SEM part number so we can be sure it's the right stuff. I know that I have used SEM vinyl products for years and they are TOP NOTCH, I have to assume their Weld-thru is too. I get "Winzer" from my guy who supplies the shop now and it's not a retail product or I would give you the number. Brian
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1948 Chevy pickup Chopped, Sectioned, 1953 Corvette 235 powered. Once was even 401 Buick mid engined with the carburetor right between the seats! Bought with paper route money in 1973 when I was 15. "Fan of most anything that moves human beings" |
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05-28-2018, 03:27 PM | #5 |
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Re: Applying weld-thru primer
Thank you all for the responses. Here is a pic of the current weld thru I'm using. Like I said I was annoyed with oreillys only having one in stock at a time and they tried telling me they didn't sell the stuff to begin with. Finally had to convince the guy to look up the part number on their site.
Anyways... Foot Stomper, I actually just meant I wear a respirator when welding with weld-thru primer. i guess I wasn't aware of needing one when welding with bare cold rolled steel :/ what's the reason for needing one in that situation? I'm still a bit confused... so let's use the interior header panel of these cabs. That is a common issue and one that I just got done doing. After it was all trimmed to fit in place I removed all the paint across the whole panel where it gets spot welded to the windshield brace. So the entire "lap" on the panel as well as the windshield brace. I then sprayed weld-thru to cover up all the bare metal which is the entire lap where the two metals will be sandwhiched together. And finally put my respirator on and start spot welding back in place. I'm just wondering if I'm doing it correctly or am I wasting weld-thru since I'm spraying this stuff throughout the entire lap instead of only the exact locations where the spot weld occurs. After reading this can of weld-thru I'm wondering if I should be putting the panel in place and marking where the spot welds will occur and spray those "dots" and a few inches both ways with weld-thru and then spray the remainder of the bare metal with a automotive primer. I hope this makes sense... I maybe should have taken a few more pics of the process to show I'm talking about. Brain, thanks for the little tid bit. I actually read that on the can which is kind of strange to me... my thoughts are that the more you have on the more protection, but this must not be true. The can states "do not over saturate" and "one light coat". |
05-28-2018, 04:29 PM | #6 |
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Re: Applying weld-thru primer
yeah I had some of mine on to thick also...it doesn't weld good that way...anything I was welding that couldn't be got to later got a coat of weldthru...I made sure to get out on the unwelded parts..that way when I blasted it, it would take the weldthru off back to the seam and then the epoxy went on the bare metal
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Mongo...aka Greg RIP Dad RIP Jesse 1981 C30 LQ9 NV4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598 Mongos AD- LS3 TR6060...http://67-72chevytrucks.com/vboard/s...34#post8522334 Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563 2023 Chevy Z71..daily driver |
05-28-2018, 07:26 PM | #7 |
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Re: Applying weld-thru primer
And if it's not fully flashed, it will weld like crap! So let it flash off.
I just did a patch this afternoon on my truck, primed it, left it outside while I came in and ate lunch went back out and welded it in. If it were winter and cold, I would have even left it until the next day. On the respirator, cold rolled, not a big deal. You probably still should, but it's not horrible. But welding on anything made after the late seventies, more and more parts were galvanized, the last 20 years or so EVERY SINGLE part is galvanized, coated in zinc. Brian
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05-28-2018, 07:28 PM | #8 |
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Re: Applying weld-thru primer
Ryan, it has no zinc or copper, so it's not your traditional weld thru, I don't know enough chemically about it to make any comments about that.
Brian
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1948 Chevy pickup Chopped, Sectioned, 1953 Corvette 235 powered. Once was even 401 Buick mid engined with the carburetor right between the seats! Bought with paper route money in 1973 when I was 15. "Fan of most anything that moves human beings" |
05-28-2018, 07:53 PM | #9 |
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Re: Applying weld-thru primer
IMO you are better off spraying an epoxy based primer on the mating flanges then grinding the weld spots to bare metal then applying weld thru on just those spots.
That Like90 is a highly regarded weld thru.
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Currently working on How To Videos and custom metal 70 Chevelle gettin Sliced and Diced Anything But STOCK 70 Chevelle SS455 not a typo its a BUICK BABY 49 and 72 Chevy Trucks restored to original...close to it Drommer Stor....Norwegian for Dream Big http://s969.photobucket.com/albums/a...lle/?start=all https://www.flickr.com/photos/47922830@N03/ Pictures of my work and projects |
05-28-2018, 08:42 PM | #10 |
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Re: Applying weld-thru primer
Thank you guys for the responses.
Brian, I had no idea about the metal composition of the newer vehicles. I appreciate the heads up. Eric, that makes perfect sense! I will do that from now on. This primer should be well saught after its $30 a can! I like it so far. The only thing Id change is the color. It is the exact match to EDP black panels. So you have to pay attention to where it's sprayed. I would rather have a gray or something so I know where I sprayed it. Can you get an epoxy in a spray can? I've just been using a good automotive primer made by Nason. One of these days I'm going to invest in an air compressor... |
05-28-2018, 09:31 PM | #11 |
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Re: Applying weld-thru primer
You can get epoxy in spray bombs but its expensive and has around a 24 hr life once used.
By far the best thing to do after welding is to flood the weld joint with epoxy. Also despite its name weld thru really is not exactly weld thru able. Once you have the panels clamped up in place ready to weld, I take a flat drill bit or small carbide bit and remove the weld thru where the weld will be.
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Currently working on How To Videos and custom metal 70 Chevelle gettin Sliced and Diced Anything But STOCK 70 Chevelle SS455 not a typo its a BUICK BABY 49 and 72 Chevy Trucks restored to original...close to it Drommer Stor....Norwegian for Dream Big http://s969.photobucket.com/albums/a...lle/?start=all https://www.flickr.com/photos/47922830@N03/ Pictures of my work and projects |
05-28-2018, 10:11 PM | #12 | |
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Re: Applying weld-thru primer
I prefer to use epoxy primer instead of weld through. IMO a catalyzed primer is going to offer better long term rust protection than anything out of a spray can. As Eric stated, I also clean the paint out of the plug weld hole using a flattened drill bit. After spot/plug welds are complete flood the area with epoxy to seal. Here's a sample of how I did a seam on a lift gate, using HOK epoxy primer..
Quote:
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05-28-2018, 10:53 PM | #13 |
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Re: Applying weld-thru primer
I really like your Specialized tool.
I will have to make one. I mean find out where to get one.LOL Thanks for the idea |
05-28-2018, 10:08 PM | #14 |
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Re: Applying weld-thru primer
the 3m primer im using is a silverish gray in color
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Mongo...aka Greg RIP Dad RIP Jesse 1981 C30 LQ9 NV4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598 Mongos AD- LS3 TR6060...http://67-72chevytrucks.com/vboard/s...34#post8522334 Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563 2023 Chevy Z71..daily driver |
05-28-2018, 11:43 PM | #15 |
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Re: Applying weld-thru primer
Awesome thanks for the heads up Greg. I will have to see if the automotive supply store has some or maybe the same brand im using in a different color.
Eric and Robert this is very interesting... why don't they tell you that in the directions? Could be why a couple of my spot welds came loose. I thought it was from over saturating the area. The way I understood it from the salesman is that you weld right on top of the stuff and the heat produces a wax that encompasses the weld to prevent corrosion. Maybe I miss understood him or didn't hear him mention drilling the primer off before welding. The heat from the weld must grab the wax from all sides and bring it in to encapsulate it then. You guys mentioned spraying epoxy over the weld... is there another product that I can get in a spray can that has a longer shelf life that is better than a standard primer? Since I don't have an air compressor I'm limited to using spray cans. The areas that will be exposed will get epoxy when it goes to the body shop, but the area I'm doing now is the top of the inner roof and drip rail braces which will be covered up after I reinstall the outer roof skin. |
05-29-2018, 06:54 AM | #16 | ||
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Re: Applying weld-thru primer
Quote:
The Weld Through primer is not really true to it's name, it will contaminate the weld. If cleaned back as Eric and I suggested, the heat from the spot weld will still liquefy the WTP surrounding the bare metal within the plug weld hole, and much like soldering copper pipes, wick toward the heat to surround the weld. Most people will use the WTP to cover the entire flange, which as you've read, is not the intent. It is not as good at rust prevention as the epoxy. Perhaps Brian can add to this, and my comments are not meant as a slight to anyone in the collision industry, but many of the products/processes recommended by I-CAR for repairs such as these also revolve around useability within a narrow window of time. You can't expect a repair to be completed within three day window if you're waiting on Epoxy primer to fully cure for seven days. If I-CAR can develop a process/use a product that still fits within their prescribed time frame for a particular repair, then the body shops are more likely to not skip a step due to what may be perceived as wasting valuable time. Having said product in a convenient spray can also makes it more likely the technician will adhere to the process and not skip a step. If Epoxy primer were used and someone needed to adhere to a seven day full cure window prior to plug welding (if that's what the process directed) then you would likely see a body shop or two that skipped that step in the interest of getting the job done in a more timely fashion. So in a similar thought that OEM spot welds aren't the best welding methods for panel attachment (these create voids for moisture and rust traps, but get the car through the assembly line much faster), I'm suggesting that the I-CAR method of using weld through primers may not be the best method for long term rust protection, but given the parameters listed above, it's the best compromise for them to insure a given standard is followed. Quote:
Why use a spray can, get some epoxy primer in quart/gallon cans and mix up what you need for what you are working on, for minimal waste. There's nothing that says you can't use brush or other similar application methods, especially those areas that will be hidden that you mention. (note the brush strokes in the green epoxy primer above) Even for exposed areas, are you not going to block out the primed surface? Be sure you still follow flash times, etc as if you were spraying. But IMO you are still using the better product even if the application method seems rudimentary. Especially for the home project, you are less concerned with the time constraint and now you would get the job done with one product throughout, eliminating the need for multiple primers.
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Robert Last edited by MP&C; 05-29-2018 at 07:03 AM. |
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05-29-2018, 09:51 PM | #17 | |
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Re: Applying weld-thru primer
Quote:
Brian
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1948 Chevy pickup Chopped, Sectioned, 1953 Corvette 235 powered. Once was even 401 Buick mid engined with the carburetor right between the seats! Bought with paper route money in 1973 when I was 15. "Fan of most anything that moves human beings" |
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05-29-2018, 05:32 PM | #18 |
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Re: Applying weld-thru primer
Get a qt of epoxy, Kirker sells qts and I believe SPI does as well.
https://www.autobodytoolmart.com/kir...r-p-12620.aspx Go to the pharmacy and ask if they will sell you plastic dosage cups. I bought a sleeve of 100 for 10 bucks, they are about the size of the clear plastic lid on a bottle of Vicks Nyquil. Mine had fluid oz marks along the side so can mix the epoxy in the correct mixture, or you can buy some cheap Stainless Steel mixing spoons.
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Currently working on How To Videos and custom metal 70 Chevelle gettin Sliced and Diced Anything But STOCK 70 Chevelle SS455 not a typo its a BUICK BABY 49 and 72 Chevy Trucks restored to original...close to it Drommer Stor....Norwegian for Dream Big http://s969.photobucket.com/albums/a...lle/?start=all https://www.flickr.com/photos/47922830@N03/ Pictures of my work and projects |
05-29-2018, 09:52 PM | #19 | |
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Re: Applying weld-thru primer
Quote:
Brian
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1948 Chevy pickup Chopped, Sectioned, 1953 Corvette 235 powered. Once was even 401 Buick mid engined with the carburetor right between the seats! Bought with paper route money in 1973 when I was 15. "Fan of most anything that moves human beings" |
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05-29-2018, 10:22 PM | #20 | |
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Re: Applying weld-thru primer
Quote:
IMG_3689 by eric2406, on Flickr IMG_3723 by eric2406, on Flickr IMG_3742 by eric2406, on Flickr
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Currently working on How To Videos and custom metal 70 Chevelle gettin Sliced and Diced Anything But STOCK 70 Chevelle SS455 not a typo its a BUICK BABY 49 and 72 Chevy Trucks restored to original...close to it Drommer Stor....Norwegian for Dream Big http://s969.photobucket.com/albums/a...lle/?start=all https://www.flickr.com/photos/47922830@N03/ Pictures of my work and projects |
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05-29-2018, 09:57 PM | #21 |
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Re: Applying weld-thru primer
These are all good ideas! I guess I never realized brushing it on works as well. I'm not really that knowledgeable about paints so this really helps! I appreciate the inputs!
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05-29-2018, 10:17 PM | #22 |
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Re: Applying weld-thru primer
Yep, and I forget about brushing it on too, damn I have a lot of catching up to do!
Brian
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1948 Chevy pickup Chopped, Sectioned, 1953 Corvette 235 powered. Once was even 401 Buick mid engined with the carburetor right between the seats! Bought with paper route money in 1973 when I was 15. "Fan of most anything that moves human beings" |
05-30-2018, 01:12 AM | #23 |
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Re: Applying weld-thru primer
Some things there are well worth the money, others are HORRID and dangerous and not worth a dime. If you pick the right ones you will be happy.
Brian
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1948 Chevy pickup Chopped, Sectioned, 1953 Corvette 235 powered. Once was even 401 Buick mid engined with the carburetor right between the seats! Bought with paper route money in 1973 when I was 15. "Fan of most anything that moves human beings" |
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