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Old 05-28-2018, 10:47 AM   #4
MARTINSR
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Join Date: Dec 2000
Location: Boise, Idaho
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Re: Applying weld-thru primer

Quote:
Originally Posted by Foot Stomper View Post
Your process is 100% correct... don't second guess yourself. You only weld thru the weld thru primer. It will keep the spot weld small, while helping to prevent corrosion after you are all done. That's why some companies call it Zinc or even copper weld thru.

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?)
LISTEN TO MR. STOMPER!

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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