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Old 04-17-2020, 11:06 AM   #13
LockDoc
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Join Date: Aug 2006
Location: Montezuma, Iowa
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Re: Where you all get your weld through primer these days?

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Copied from the H.A.M.B.

Weld thru primer is used in modern collision repair to replace the zinc coating imbedded in modern sheet metal, only when it is ground off during the repair. It was designed to be used ONLY on bare metal mating flanges. And YES you weld right through it. Absolutely NOT for use on the inside of enclosed panels.

It has very poor adhesion properties. It WILL fail and peel if used on surfaces other than the inside flanges in a pinch weld. It's one of the most misunderstood, and misused products in the industry. Some manufactures do not even allow it in their repair procedures at all.

It works by galvanic corrosion. The zinc or copper corrodes and forms a "seal" against further corrosion, rather than breaking down like steel corrosion. When a plug weld is made on a pinch type flange the primer liquefies and then has some ability to "wick" back in around the weld. It's a "better than nothing" product. The joint still must be sealed completely after welding or it will still corrode. It's just a PART of the corrosion protection process used in modern collision

That said, I use it in both modern collision and restoration, but only where its "pinched"
between two pieces of steel. I prefer the copper from UPOL. I think it has less effect on the weld, than the zink. Tests I've read claim both are about the same in their "limited" corrosion protection.

And Another:

Tin bender is on the money, ICAR is in flux about both though as its been suggested they actually cause corrosion.

There is a new product from Valveoline which you spray on the edge of the pieces of metal after welding the bare metal. It creeps in between the pieces & surrounds the weld with a polymer which blocks moisture. They have a few products in that line. When I took the class for ultra high tensile strenth steel repairs they mentioned that it may be the future type of product to replace copper/zinc weld through primers.
we tried it at our shop but the manager was to cheap to purchase. Hes waiting for it to be mandated, like most everything else.

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