Hey Guys, I would like to know the difference between copper or Zinc weld thru primer. I would like to know what is preferred and why. Is one more toxic than the other? Thanks again for any info.
I don't know too much about weld thru primers,I still adhere to the way I was instructed many years ago and work with bare metal,,if the raint or primer is present I grind it off. HRP
Weld through primer goes on the backside of what you are welding and leaves a protected surface after you weld, you don't actually weld "through" the primer. This is used in places where you cannot get to after you are done welding like rocker panels. I don't know if one is more toxic than the other. Posted using the Full Custom H.A.M.B. App!
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.
^^ Exactly what he said. The only thing I can add is the copper is probably a little less toxic in the air when welding than zinc.
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 cl*** 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.
So I have a set of floor panels that are completely covered in weld through primer. Will I have to remove this product entirely before I can paint these floors?
Only if you want to to stick You'll get varied opinions here......on everything! But all the weld thru primers I'm aware of have poor adhesion. I think epoxy is the best bet. Good news is, it can be brushed. That's how I do inner rockers most of the time. Then I clean just the weld site, and use weld thru there if its a pinch weld. For plug welds I clean about an inch, so it's a small amount of weld thru. Metal has to be cleaned and sanded just like it was an outer panel. Otherwise your wasting time and materials. I like to use a self etch, then epoxy, but they have to be compatible. Not all are.
I've used the Upol copper and it was great. I bought some NAPA zinc weld through and it caused my plug welds to explode while welding. I don't know if it was the zinc or the NAPA brand that caused this to happen, it doesn't matter now because I threw the can in the garbage to ensure I didn't use it again. Dave
Zinc weld through causes a little more splatter than copper, I've never had any problem using any of them, I guess there's a price difference in favor of zinc. I also sometimes use the zinc as a light coat to protect bare metal on parts that will be stored for a long time in not ideal conditions, remember it's not rust proof, then just wash it off when it's time for paint.
I bought these panels from Dennis Carpenter. They are totally covered in weld through. There are few if any welds to be anywhere other than the perimeter areas. When Drake offered the panels they came in the black coating you see on oem panels. I would have preferred bare metal. remvoing all this primer will a real pain!
The United Pacific parts are coated with the same product. I have been sanding it off in select areas when welding, and on the pinch welds using the copper spray.
Are you sure it's weld thru primer or are they lightly galvanized ? Called galvaneal in modern sheet metal. If so, and it's adhered well, I wouldn't remove it. If it's just weld thru primer it will wipe off with most solvents. I had some cab corners come with it. I didn't like it. It's a pita gas welding. In that case it seemed to be adhered well, but by the time I had them fit and finished most of it was gone from the outside surface.
If those panels are a Silvery colour, it`s Galvaneal. If they are Black, it is most likely EDP or similar. Almost like a powdercoat in it`s reaction. I sand off all the areas to be welded, as it will contaminate some. You can weld over it, but the fumes are not good for you. Not near as bad as Zinc or Galvaneal,but still. I don`t use Weld-Thru primer, but I`ve always tried to coat the back sides of my repair to help somewhat. I usually just use a cheap spraycan primer, and avoid spraying where I am welding (fumes again) I coat after the weld is worked and file finished on the back side, and use DX 79 Metalprep on the outside. All my work leaves the Shop in Bare metalprepped steel, so the customer and Painter can see what they have......
The boxes the panels came in from Carpenter are boldly marked, " weld through primer". I cannot imagine why they would coat the entire surface with a product that would have to be removed before any kind of painting. I will give them a call tomorrow and see what they have to say regarding this matter. I expect little help from them as these parts are stamped offshore and probably coasted there also before shipping. No big deal really, just another project setback a**** many others.
Weld through wipes off with thinner. Galvonized metal is toxic so grind it off where your welding, & use a mask along with good ventilation.
I know it's an old thread. I have a back ground in the marine industry and experience with galvanic corrosion. Based on that back ground, I would be highly skeptical that copper based paint would be a good idea for steel. Any dissimilar metals set up a battery / galvanic cell. In a galvanic cell, one metal will be protected, the other will be sacrificed (corroded). There is a table called the Galvanic series which shows the relative position of the metals, their corresponding voltage potential, and which one is protected and which is sacrificed. Zinc and steel is very good because the zinc is sacrificial and protects the steel from corrosion. In addition, zinc also forms a pretty impervious surface after it has weathered. That is why galvanizing is such a good protective surface. Copper and steel is one of the worst combinations you can have. Copper will be protected at the expense of the steel. In a pinch weld, the moisture will get in their and the copper will accelerate the rust. Incidentally, this is the same reason Chrome bumpers rust under the chrome and the plating comes off. (Chromium and nickel are the wrong metals for steel). If the chrome is thick enough, you have a chance of preventing the galvanic cell by keeping the moisture out. Today's chrome bumpers are so thin, that the moisture gets in and the chrome plating actually causes a galvanic corrosion problem. I would have the same concerns with the copper anti seize that I see is now available. Aluminum (old style anti seize ) is compatible with steel. Sent from my iPhone using H.A.M.B.
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