Hot Rods Plug weld over por15?

The underlining panel has por15. Can I plug weld another panel right on top of the por15 with the por15 in the plug weld hole?

 

No, you must have clean metal or use a weld through primer.

 

If the area being underlapped/ plug welded to is already painted, what i do is drill the plug holes in the overlapping piece and get it lined up where its going to be welded to and mark off those spots and kiss those spots with a round die grinder bit to remove just the spot thats being welded to. Then when you line it back up, theres bare metal that can be plug welded to, kind of a poor man's spot weld. I havent really found a weld through primer that i like, so this is what i do instead. I scrounged up some old pictures from when i was doing a floor

 

Weld through primer acts like something’s on the metal ? Because , well something is on the metal !!!

 

Not to mention the isocyanates in POR.....I wouldn't want to be breathing that*****.

 

I’d do like Stooge even when I use weld-through primer. I don’t need something hampering my weld strength or aesthetics.

 

Weld through primers are for resistance spot welding. For mig plug welding, they should be scraped/cleaned from the base panel. Once they are clamped together.

The copper based weld through primers work much better for mig welding. Than the zinc based ones do, imho.

 

What would happen to the plug weld if there is por15 in the plug weld hole and the weld is attempted?

 

Grind it off, and wear a respirator.

The risks of isocyanates was brought to the world's attention with the 1984 Bhopal disaster, which caused the death of nearly 4000 people from the accidental release of methyl isocyanate. In 2008, the same chemical was involved in an explosion at a pesticide manufacturing plant in West Virginia.[20]

LD50s for isocyanates are typically several hundred milligrams per kilogram.[21] Despite this low acute toxicity, an extremely low short-term exposure limit (STEL) of 0.07 mg/m3 is the legal limit for all isocyanates (except methyl isocyanate: 0.02 mg/m3) in the United Kingdom.[22] These limits are set to protect workers from chronic health effects such as occupational asthma, contact dermatitis, or irritation of the respiratory tract.[23]

 

Um, you weld much? Not being rude but welding requires good, clean electrically conducive contact. Surgically clean if you desire good welds. POR-15 (besides being a nasty health hazard is not a conductor of electricity; it would be like welding plastic to steel. And that's no bueno

 

On another panel there is undercoat on the back side. Should the undercoat be removed before***** welding?

 

Maybe consider some type of body panel adhesive for "over laps".
Anything that can trap water in between panels makes me nervous. I'm not saying that's what you're doing. I just mean in general.

 

Yes. It will contaminate your***** weld, if you don't remove it.

 

What could this contamination do? More likely to rust? Less strong? On some panels it may not be possible to get behind and remove the undercoating.

 

They say there's no such thing as a silly question but...


Sorry, maybe this***** is too obvious. Sometimes I can't help myself.

 

If you can't get to it, how did it get "undercoated"? It could give you porosity and weaker welds. That is the main thing. Everybody here has welded panels that they couldn't get to the backside of but I've never seen any that were undercoated on the backside? Z-bart? If that's the case, you'll just have to pay your money and take your chances.

 

If your asking questions like this maybe it's a good.. no great idea to find someone who actually knows how to weld and have them do it. Especially if it's structural (floor pans, rockers, etc).

It's very simple, to have solid, strong, supporting welds ALL metal involved in that weld need to be clean, rust free, undercoat free, paint free, etc, again it needs to be shiny clean.

It's really that simple, if you don't care that there is NO penetration, welds look like mud dobber nests instead of small puddles, what welds actually did melt together will quickly break from simple flex from driving and squeaks and pop noises while driving and last but not least, that there is absolutely no structural integrity in the seams or welds then by all means go ahead and try welding it all together....


...

 

Contamination of your weld pool can result in inclusions, porosity, poor penetration, and poor fusion. None of which do you want in your weld, it all comes down to a poor and likely weak weld prone to failure. If you can't clean both sides to clean metal, make another plan for attaching them.

The questions you're asking sound like you're a novice at welding. If that's the case you should either practice a lot or find someone that can help you with it.

 

I questioned the welder at the restoration shop. I suspect I could do a better job myself at this.

 

Rubberized undercoat on the back side will burn off due to the high heat required to melt steel together. It will smell and it may burn, a wet rag will douse the flames. Undercoating is petroleum based and will burn

 

Is it rubberized undercoating. So is it ok to***** weld with the rubberized undercoating on one side?

 

For rosette/“plug” welding I tip I learned a while back is to take a drill bit the same size as the holes on the top layer. Bring the drill bit flat and while the top layer is clamped tightly “drill” the offending material off to give a nice clean area to weld to.

 

Looks like old_chevy just wants our permission to do what is easy. I have a similar problem currently. Helping a friend work on a truck that has rather questionable previous work. I need to weld up a seam but someone had slathered some tar like undercoating substance over the seam. I try to clean it the best I can and get everything to bare metal but welding produces heat and more of this stuff leaks out from under the seam to contaminate the weld. We are always at the mercy of whoever worked on the car before us.

 

they use steel paint/primer at my shop... forgot what it's called...

 

it's called "steel it"

 

Amazon.com: Steel-It 1012D Polyurethane, Industrial Paint Coatings, Weldable, Easy to Apply - Black (1 Pack) : Industrial & Scientific

 

The Bandit said it all . I have been a welder for many years , stick , MIG ,TIG cleanliness is next to Godliness when it comes to welding . Even where the ground clamp attaches , needs to be spotless . Most welding circuit is DC so current must flow in a circle . You have went this far , it you don’t have enough time to do it the best as you possibly can , how do you have enough time to do it over again later .
My new way of attaching panels today is with new structural adhesives . If the panels are over lapped it’s hard to beat .

 

I have noted on a few occasions when my ground clamp is on questionable metal it gets HOT! Too hot to touch. Thats resistance to the "loop" you mentioned.

I was watching that "forged in fire" show the other night. Guys were forge welding (san mai, Damascus, etc) without cleaning the steel. It doesn't work unless it is clean, very clean. It doesn't work making knives, it doesn't work building hot rods.

 

Forge welding is what I've considered "Hammer Welding". How swords etc. were made long before you or I were around. Heat the metal good and hot, layer with different properties, hammer, and voila!

I know most people believe hammer welding is metal finishing or hammering their welds but if they check in to the history books they will get a better understanding.

 

I'm paying a restoration shop to do the work. The restoration shop is not cleaning the welds. When I welded I always took care to clean the welds. Shop says it is not a problem and the undercoating burns always during welding. I'm not a professional.