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oscarsnapkin Samba Member
Joined: October 22, 2013 Posts: 557 Location: Bucks County, PA
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Posted: Fri Oct 15, 2021 12:27 pm Post subject: Why Can’t I Weld Through My Weld-Thru Primer??? |
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The title says it all. I applied POR15 weld-thru primer to the lip around my Thing chassis (the part that the floorpans rest on) and also to the bottom side of my new pans (I applied about an inch wide stripe to match up with where the pans would be welded to chassis). Tried welding the pan to the chassis and nothing will stick to the primer. The weld will stick to the top of my pans that are bare metal, but that’s it. I tried wire brushing off the primer in a spot and it welded fine. I thought perhaps the can of primer that I had was crap, so I bought a can of Eastwood Self-Etching Weld-Thru Primer. I sandblasted the chassis to remove the old primer, applied the new stuff, and I am having the exact same issue. I will openly admit that I am a novice welder, but I’ve practiced enough that I shouldn’t be having this much trouble. Do I need to adjust the welder settings? Any ideas would be great, because I can’t stand the idea of having to strip all this primer off again. Thanks. _________________ - 1977 CEI Sunroof Bus 2.0L F.I. Hydraulic Lifters
- 1973 Thing
"It’s so easy to laugh, it’s so easy to hate, it takes strength to be gentle and kind." |
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VW_Jimbo Samba Member
Joined: May 22, 2016 Posts: 9880 Location: Huntington Beach, CA
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Posted: Fri Oct 15, 2021 3:08 pm Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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I am hoping I am reading this correct and you have a MIG welder. I am no expert but I have learned several things along my journey.
I only use Copper weld through primer. And even that sometimes is hard to get to start a weld on. Sometimes I have to scrap the wire on the primed surface to get the arc started.
The next thing has been to be sure the ground clamp is grabbing onto CLEAN STEEL! That is a BIG ONE!
The next is the wire itself. If it is old, it may have oxidized and will not start easily. A fresh new wire roll will help, dramatically!
And then the biggest issue I read about, turn up the heat range! Always worth trying! Worst case is blowing through the steel, but then you at least know the machine works!
Good luck! Hope one of those ideas helps you out! _________________ Jimbo
There is never enough time to do it right the first time, but all the time necessary the second time!
TDCTDI wrote: |
Basically, a whole bunch of fuckery to achieve a look. |
67rustavenger wrote: |
GFY's Xevin and VW_Jimbo! |
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raydog Samba Member
Joined: February 09, 2006 Posts: 1157 Location: Cape Cod
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Posted: Fri Oct 15, 2021 3:41 pm Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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I was having the same problem. What I ended up doing, was drill thru the pan and into the lip on the chassis where you want to lay a weld. On the chassis drill deep enough to create a divot in the steel. Don't try and lay a constant bead. Turn up the heat. Then start your spot weld in the divot and pool the metal. The pan will get hot enough and the pool will adhere to the pan. In other words, start the weld on the chassis and pool up to the pan. I forgot what size drill bit I used, try around 1/4" or slightly smaller.
What is happening with you is that you are not getting the heat down to the thicker metal. No penetration. _________________ Come on, It's not rocket science. KISS |
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viiking Samba Member
Joined: May 10, 2013 Posts: 2666 Location: Sydney Australia
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Posted: Fri Oct 15, 2021 4:33 pm Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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^^^^This.
Just get even a small divot through the primer and turn up your settings a notch.
Whilst the primer is conductive because of the copper or zinc in the formula, there is still other relatively non-conductive paint binders holding it all together. You need to get an earth path through the primer either by scratching the surface or turning the heat up.
The only issue with the latter is that, once through the primer, you may have too much power and end up blowing through the steel. I would just try the drill or scratch method first and see how you go. _________________ 1968 1500 RHD Lotus White Beetle since birth. In the hospital for major surgery
1966 Lancia Flavia Pininfarina Coupe - in the waiting room
Discharged: 1983 Vanagon, 1974 1800 Microbus,1968 Low Light,1968 Type 3 |
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wheel607 Samba Member
Joined: May 30, 2004 Posts: 1845
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Posted: Sat Oct 16, 2021 12:25 am Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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Again, turn up the heat and also make sure it is GROUNDED........more problems from improper grounding than anything else. |
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oscarsnapkin Samba Member
Joined: October 22, 2013 Posts: 557 Location: Bucks County, PA
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Posted: Sat Oct 16, 2021 12:45 pm Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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To answer VW Jimbo, yes, using a MIG welder. Definitely know it works. However, the wire is at least 3-4 years old, so I will try using a fresh spool. The wire has worked great on non-primered applications. Regardless, a new spool won’t go to waste so it is worth trying. I inadvertently have done the ‘divot’ method with a drill as was mentioned above. I was drilling a hole in the pan and it went through slightly to the frame. I didn’t have any luck, but by that point I had more or less had enough for the day. I will give these suggestions a shot next week and post a follow up. Thanks as always. _________________ - 1977 CEI Sunroof Bus 2.0L F.I. Hydraulic Lifters
- 1973 Thing
"It’s so easy to laugh, it’s so easy to hate, it takes strength to be gentle and kind." |
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evanfrucht Samba Member
Joined: July 24, 2016 Posts: 2180 Location: Laurel Canyon, CA
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Posted: Sat Oct 16, 2021 9:35 pm Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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Weld thru primer is useless BS
X2 the only halfway usable type is copper and not available to the general public...
Brush or sand it off or just melt the hell thru it with excessive heat.
Live and learn... I hate that stuff _________________ 1967 Bug ( the daily rod )
1964 Fury Wagon ( the pavement shredder ) |
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infiniteLoop Samba Member
Joined: October 09, 2020 Posts: 265 Location: Empire State
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Posted: Sun Oct 17, 2021 5:56 pm Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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I've tried weld through primer and thought it was a gimmick. If you can't get a decent arc through the primer remove a small area of it. As far as welding contaminated dirty metal, If you push the pool, it will have no issues with lots of rust so primer might act the same way. If the primer is burning off it will displace the shielding gas so try to see if that is happening. I once read that fence paint, or spray galvanization worked pretty good as well and it seemed to but you have to make sure you don't get poisoned by the zinc. Also , I tried high heat paint and the results were not that bad. |
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Bulli Klinik Samba Member
Joined: January 16, 2005 Posts: 2065 Location: Bulli Klinik, Colorado Springs
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Posted: Mon Oct 18, 2021 7:31 am Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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For rosette welds, I max out my Lincoln 180 on the highest setting. Practice a little on some scrap. _________________ I've never met a Bus I didn't like.
Mike K
Bulli Klinik
Colorado Springs |
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scrivyscriv Samba Electrician
Joined: October 04, 2011 Posts: 2918 Location: Memphis
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Posted: Mon Oct 18, 2021 9:36 pm Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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3M has a channel on youtube with technical information videos.. very helpful!! I highly recommend searching through their series. Here are some related to your primer question.
Link
Link
Link
_________________ Robert in Memphis
Dünkelgrügen 1967 Java Green bug thread
Engine rebuild thread
If you're ever in the Memphis area, you are welcome to stop by for advice and help. |
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VW_Jimbo Samba Member
Joined: May 22, 2016 Posts: 9880 Location: Huntington Beach, CA
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Posted: Wed Oct 20, 2021 1:15 pm Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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evanfrucht wrote: |
Weld thru primer is useless BS
X2 the only halfway usable type is copper and not available to the general public...
Brush or sand it off or just melt the hell thru it with excessive heat.
Live and learn... I hate that stuff |
I have tried burning it off. If I dont go blowing holes through the two parts I want to weld together, I will instead get them to weld together and then get an odd reaction from the weld puddle. I call them stalagmites. They look like worm holes that grow upwards out of the puddle. Some of them are hollow bubbles. Really odd and weird! The only item I can contribute to this issue is the copper weld through primer. I have learned to use the divot method. Works awesome! _________________ Jimbo
There is never enough time to do it right the first time, but all the time necessary the second time!
TDCTDI wrote: |
Basically, a whole bunch of fuckery to achieve a look. |
67rustavenger wrote: |
GFY's Xevin and VW_Jimbo! |
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oscarsnapkin Samba Member
Joined: October 22, 2013 Posts: 557 Location: Bucks County, PA
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Posted: Tue Oct 26, 2021 3:21 pm Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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Bulli Klinik wrote: |
For rosette welds, I max out my Lincoln 180 on the highest setting. Practice a little on some scrap. |
Does the wire speed need to be adjusted as well? So as a follow up, I removed all traces of the weld-thru primer with acetone and set the welder to its max setting (I left wire speed at its recommended setting of 2.5 for 14 gauge). Thinking this would solve my problem, I made another attempt at getting these pans to weld to the chassis….and another, and another. All with the same results. The weld sticks to the pan great and appears to be attached to the chassis, but with a slight bang on the bottom of the pan the weld immediately pops off the frame. It’s a pain in the ass because I then have to grind/smooth out the bad ‘welds.’ The leftmost weld in the picture below is one that I made after having made the adjustments. The one on the right is an old one that I have not finished grinding down. I’ve been using a 1/4” drill bit to drill the holes into the pan and making a divot in the chassis lip. I tried the welder on a piece of 14ga. scrap using the same settings and it seems to have worked great. Could the fact that my frame is sandblasted affect the weld quality? Any ideas or thoughts on something I might be overlooking? Thanks.
_________________ - 1977 CEI Sunroof Bus 2.0L F.I. Hydraulic Lifters
- 1973 Thing
"It’s so easy to laugh, it’s so easy to hate, it takes strength to be gentle and kind." |
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infiniteLoop Samba Member
Joined: October 09, 2020 Posts: 265 Location: Empire State
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Posted: Tue Oct 26, 2021 4:44 pm Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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Quote: |
Does the wire speed need to be adjusted as well? |
If you go that route of welding too hot than the answer is yes.
Quote: |
the weld immediately pops off the frame. |
You are refering to cold fusion. There are other threads that address this. By keeping the nozzle stationary the pool is being forced to flow over where the desired weld is. Does not mean the pool will fuse though. |
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LAGrunthaner Samba Member
Joined: March 18, 2007 Posts: 5501 Location: 1st Coast
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Posted: Sun Dec 19, 2021 1:08 pm Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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Great video by 3M. I’ve always thought weldable spray products were strange and would never do it. I was always taught to only weld bare metal.
Looking forward to their other videos. I especially like their tiny belt sander and what kind of clamps was he using?
scrivyscriv wrote: |
3M has a channel on youtube with technical information videos.. very helpful!! I highly recommend searching through their series. Here are some related to your primer question.
Link
Link
Link
|
_________________ American Red Cross Safe And Well:
https://www.redcross.org/about-us/news-and-events/...bsite.html
Maui Roadsters
www.mauiroadsters.com
http://www.oacdp.org
Lind wrote: |
Have you considered simply starting with a nicer bus? I don't know what your skills are, but the race is easier if you can see the finish line. If you are not a runner, don't start off doing a marathon. |
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viiking Samba Member
Joined: May 10, 2013 Posts: 2666 Location: Sydney Australia
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Posted: Sun Dec 19, 2021 4:15 pm Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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VW_Jimbo wrote: |
evanfrucht wrote: |
Weld thru primer is useless BS
X2 the only halfway usable type is copper and not available to the general public...
Brush or sand it off or just melt the hell thru it with excessive heat.
Live and learn... I hate that stuff |
I have tried burning it off. If I dont go blowing holes through the two parts I want to weld together, I will instead get them to weld together and then get an odd reaction from the weld puddle. I call them stalagmites. They look like worm holes that grow upwards out of the puddle. Some of them are hollow bubbles. Really odd and weird! The only item I can contribute to this issue is the copper weld through primer. I have learned to use the divot method. Works awesome! |
My theory for the stalagmites is probably the same principle as slag floating on molten steel. The melting point of copper (plus any non metallic ingredients) is much lower than molten steel. As steel melts in the molten pool of the arc, all the more volatile ingredients are blown out of the molten pool just the same as a volcano. That is, they boil. As the "magma" is blown out, it creates a protrusion of sorts where there is a gaseous vent which allows a thinner layer of steel to be quickly cooled, hence your "stalagmites".
The interesting thing about weld through primer is that it is probably ineffective at the centre of the weld pool out and part of the way of the Heat Affected Zone as the copper has probably migrated away. How far out depends on where the temperature of the HAZ at any point is below the MP of Copper.
So you are probably left with very clean steel which starts to rust immediately at the microscopic level. Hence why you need to seal the surface to TRY and reduce the level of air and water. _________________ 1968 1500 RHD Lotus White Beetle since birth. In the hospital for major surgery
1966 Lancia Flavia Pininfarina Coupe - in the waiting room
Discharged: 1983 Vanagon, 1974 1800 Microbus,1968 Low Light,1968 Type 3 |
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VW_Jimbo Samba Member
Joined: May 22, 2016 Posts: 9880 Location: Huntington Beach, CA
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Posted: Sun Dec 19, 2021 10:31 pm Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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viiking wrote: |
VW_Jimbo wrote: |
evanfrucht wrote: |
Weld thru primer is useless BS
X2 the only halfway usable type is copper and not available to the general public...
Brush or sand it off or just melt the hell thru it with excessive heat.
Live and learn... I hate that stuff |
I have tried burning it off. If I dont go blowing holes through the two parts I want to weld together, I will instead get them to weld together and then get an odd reaction from the weld puddle. I call them stalagmites. They look like worm holes that grow upwards out of the puddle. Some of them are hollow bubbles. Really odd and weird! The only item I can contribute to this issue is the copper weld through primer. I have learned to use the divot method. Works awesome! |
My theory for the stalagmites is probably the same principle as slag floating on molten steel. The melting point of copper (plus any non metallic ingredients) is much lower than molten steel. As steel melts in the molten pool of the arc, all the more volatile ingredients are blown out of the molten pool just the same as a volcano. That is, they boil. As the "magma" is blown out, it creates a protrusion of sorts where there is a gaseous vent which allows a thinner layer of steel to be quickly cooled, hence your "stalagmites".
The interesting thing about weld through primer is that it is probably ineffective at the centre of the weld pool out and part of the way of the Heat Affected Zone as the copper has probably migrated away. How far out depends on where the temperature of the HAZ at any point is below the MP of Copper.
So you are probably left with very clean steel which starts to rust immediately at the microscopic level. Hence why you need to seal the surface to TRY and reduce the level of air and water. |
Really respect your take on stuff! Really glad you like typing.
Mini volcanoes! How cool is that!
So....that weld thru primer is BS? I have watched several videos which show how it helps. But, if it really does not....that would make shit easier to weld.
What and how do you prepare before welding, to prevent rust from starting? What and how, do you do, to the weld after welding, to keep rust in check?
I am starting to believe, that the only thing to do is to have the car “ dipped” after everything is finished being welded.
Interested in your 2 cents. Thanks! _________________ Jimbo
There is never enough time to do it right the first time, but all the time necessary the second time!
TDCTDI wrote: |
Basically, a whole bunch of fuckery to achieve a look. |
67rustavenger wrote: |
GFY's Xevin and VW_Jimbo! |
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viiking Samba Member
Joined: May 10, 2013 Posts: 2666 Location: Sydney Australia
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Posted: Mon Dec 20, 2021 3:23 pm Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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VW_Jimbo wrote: |
viiking wrote: |
VW_Jimbo wrote: |
evanfrucht wrote: |
Weld thru primer is useless BS
X2 the only halfway usable type is copper and not available to the general public...
Brush or sand it off or just melt the hell thru it with excessive heat.
Live and learn... I hate that stuff |
I have tried burning it off. If I dont go blowing holes through the two parts I want to weld together, I will instead get them to weld together and then get an odd reaction from the weld puddle. I call them stalagmites. They look like worm holes that grow upwards out of the puddle. Some of them are hollow bubbles. Really odd and weird! The only item I can contribute to this issue is the copper weld through primer. I have learned to use the divot method. Works awesome! |
My theory for the stalagmites is probably the same principle as slag floating on molten steel. The melting point of copper (plus any non metallic ingredients) is much lower than molten steel. As steel melts in the molten pool of the arc, all the more volatile ingredients are blown out of the molten pool just the same as a volcano. That is, they boil. As the "magma" is blown out, it creates a protrusion of sorts where there is a gaseous vent which allows a thinner layer of steel to be quickly cooled, hence your "stalagmites".
The interesting thing about weld through primer is that it is probably ineffective at the centre of the weld pool out and part of the way of the Heat Affected Zone as the copper has probably migrated away. How far out depends on where the temperature of the HAZ at any point is below the MP of Copper.
So you are probably left with very clean steel which starts to rust immediately at the microscopic level. Hence why you need to seal the surface to TRY and reduce the level of air and water. |
Really respect your take on stuff! Really glad you like typing.
Mini volcanoes! How cool is that!
So....that weld thru primer is BS? I have watched several videos which show how it helps. But, if it really does not....that would make shit easier to weld.
What and how do you prepare before welding, to prevent rust from starting? What and how, do you do, to the weld after welding, to keep rust in check?
I am starting to believe, that the only thing to do is to have the car “ dipped” after everything is finished being welded.
Interested in your 2 cents. Thanks! |
Thanks Jimbo. I think the respect with VW is actually towards your experience not mine!
I'm a (retired) chemist/chemical engineer, and as a scientist used to postulating a theory and then proving that the theory is correct by experimentation.
In this case I have NO proof, only theory. Until I see documented proof that weld through primer works, then I have to say it doesn't, but it could.I have to be skeptical.
My speculation as I said above is that the temperature in the arc pool is higher than the melting point of steel. The MP of steel is ~2500F (1370C) and the MP of Copper is ~1980F (1080C) whilst Zinc is ~787F(420C).
So regardless of which type you use, the Copper or Zinc elements will melt along with the steel and (edit) “the steel will cool first”. So where are they deposited? If they are deposited on top of the cooled steel and coats it perfectly then it will work. If the Copper or Zinc produce some sort of new alloy with the steel which imparts anti-rust then it will work. If it migrates away from ANY of the steel and leaves bare steel, then it will not work.
I would expect you need some very sophisticated spectroscopy to determine whether the steel has been protected. Hopefully there is a metallurgist on this site that might add their expertise for this.
So what do I do? I've tried some zinc based weld through primer and just think it is not worth the hassles of getting an arc. I clean my welds after they have been ground down with phosphoric acid, rinse and dry each welded area. Then if needed I will use fibreglass body filler to seal up pinholes or use a polyurethane paint like KBS Rust Seal or Master Series to paint over the welded area on both sides if it is not a cosmetic repair. Some use epoxy primer, that's OK too especially on a cosmetic repair. For a cosmetic repair, I try and get the weld as smooth and without pinholes that I can, even if that takes numerous weld/grind cycles.
You have to do BOTH sides of the weld, not just the side you see. How you do that requires some ingenuity sometimes. I've coated the inside of my new heater channels before installation by sloshing paint inside them before welding them in, then using a cheap bore camera to look at the HAZ of the welds and then painting over the top of them to try to seal it from the atmosphere. You just have to try and do something!
The important thing is that you seal the weld area after welding. Rust has to have water and air to work. Water has a small amount of oxygen dissolved in it, so steel can still rust in the total absence of "air". So seal any exposed steel to slow but never eliminate the rust process. If you do a good job on sealing the steel, the rusting will be at microscopic levels and not cause any issue with paint interactions. If you are lazy or sloppy then the result will be bad.
The Titanic sits at the bottom of a cold salty ocean. It has relatively minimal rust given how long it has been exposed to water. Even in cold water there is still some oxygen, but not enough for the rust process to completely destroy the steel.
These days of course cars come with steel that has some sort of galvanised base. New cars do not rust like the cars that I was bought up with from the '60's which were rusting on the dealership lot! VW tried dipping our cars, but this did little to seal folded seams.
The companies pedalling weld through primer are out to make a dollar. There may be evidence that will satisfy my skepticism, but I haven't seen it yet. If someone has it, then I'm happy to be educated.
Well that's a few cents worth and hope it partly explains my position.
And yes I write a lot. It's in the nature of my profession. _________________ 1968 1500 RHD Lotus White Beetle since birth. In the hospital for major surgery
1966 Lancia Flavia Pininfarina Coupe - in the waiting room
Discharged: 1983 Vanagon, 1974 1800 Microbus,1968 Low Light,1968 Type 3
Last edited by viiking on Sat Dec 25, 2021 2:19 pm; edited 1 time in total |
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viiking Samba Member
Joined: May 10, 2013 Posts: 2666 Location: Sydney Australia
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Posted: Mon Dec 20, 2021 3:48 pm Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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PS. What do I do before welding? Remove any thinned area, pitted area and weld in some new steel. There's no point trying to repair thinned or partly rust steel.
Even with a MIG, whilst you can weld in a not so clean substrate, I make sure all of my weld areas are clean down to shiny surface. _________________ 1968 1500 RHD Lotus White Beetle since birth. In the hospital for major surgery
1966 Lancia Flavia Pininfarina Coupe - in the waiting room
Discharged: 1983 Vanagon, 1974 1800 Microbus,1968 Low Light,1968 Type 3 |
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modok Samba Member
Joined: October 30, 2009 Posts: 26743 Location: Colorado Springs
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Posted: Wed Dec 22, 2021 10:42 pm Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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the name is misleading. It should be "weld near" primer. |
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LAGrunthaner Samba Member
Joined: March 18, 2007 Posts: 5501 Location: 1st Coast
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Posted: Thu Dec 23, 2021 3:10 am Post subject: Re: Why Can’t I Weld Through My Weld-Thru Primer??? |
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Professor viiking, I love your writings. I find this statement interesting regarding folded steel which is on all or vehicles. Do you think the above 3M video regarding the seam sealer is the best way to keep that air out of the folds? I prefer all my repairs butt welded but I have some other projects that I'll need to overlap like in the 3M video and not a fan of that method. My VW is fine but I have other projects that I'd like to MIG this spring.
Happy Holidays,
Linda
"VW tried dipping our cars, but this did little to seal folded seams."
viiking wrote: |
VW_Jimbo wrote: |
viiking wrote: |
VW_Jimbo wrote: |
evanfrucht wrote: |
Weld thru primer is useless BS
X2 the only halfway usable type is copper and not available to the general public...
Brush or sand it off or just melt the hell thru it with excessive heat.
Live and learn... I hate that stuff |
I have tried burning it off. If I dont go blowing holes through the two parts I want to weld together, I will instead get them to weld together and then get an odd reaction from the weld puddle. I call them stalagmites. They look like worm holes that grow upwards out of the puddle. Some of them are hollow bubbles. Really odd and weird! The only item I can contribute to this issue is the copper weld through primer. I have learned to use the divot method. Works awesome! |
My theory for the stalagmites is probably the same principle as slag floating on molten steel. The melting point of copper (plus any non metallic ingredients) is much lower than molten steel. As steel melts in the molten pool of the arc, all the more volatile ingredients are blown out of the molten pool just the same as a volcano. That is, they boil. As the "magma" is blown out, it creates a protrusion of sorts where there is a gaseous vent which allows a thinner layer of steel to be quickly cooled, hence your "stalagmites".
The interesting thing about weld through primer is that it is probably ineffective at the centre of the weld pool out and part of the way of the Heat Affected Zone as the copper has probably migrated away. How far out depends on where the temperature of the HAZ at any point is below the MP of Copper.
So you are probably left with very clean steel which starts to rust immediately at the microscopic level. Hence why you need to seal the surface to TRY and reduce the level of air and water. |
Really respect your take on stuff! Really glad you like typing.
Mini volcanoes! How cool is that!
So....that weld thru primer is BS? I have watched several videos which show how it helps. But, if it really does not....that would make shit easier to weld.
What and how do you prepare before welding, to prevent rust from starting? What and how, do you do, to the weld after welding, to keep rust in check?
I am starting to believe, that the only thing to do is to have the car “ dipped” after everything is finished being welded.
Interested in your 2 cents. Thanks! |
Thanks Jimbo. I think the respect with VW is actually towards your experience not mine!
I'm a (retired) chemist/chemical engineer, and as a scientist used to postulating a theory and then proving that the theory is correct by experimentation.
In this case I have NO proof, only theory. Until I see documented proof that weld through primer works, then I have to say it doesn't, but it could.I have to be skeptical.
My speculation as I said above is that the temperature in the arc pool is higher than the melting point of steel. The MP of steel is ~2500F (1370C) and the MP of Copper is ~1980F (1080C) whilst Zinc is ~787F(420C).
So regardless of which type you use, the Copper or Zinc elements will melt along with the steel and will cool first. So where are they deposited? If they are deposited on top of the cooled steel and coats it perfectly then it will work. If the Copper or Zinc produce some sort of new alloy with the steel which imparts anti-rust then it will work. If it migrates away from ANY of the steel and leaves bare steel, then it will not work.
I would expect you need some very sophisticated spectroscopy to determine whether the steel has been protected. Hopefully there is a metallurgist on this site that might add their expertise for this.
So what do I do? I've tried some zinc based weld through primer and just think it is not worth the hassles of getting an arc. I clean my welds after they have been ground down with phosphoric acid, rinse and dry each welded area. Then if needed I will use fibreglass body filler to seal up pinholes or use a polyurethane paint like KBS Rust Seal or Master Series to paint over the welded area on both sides if it is not a cosmetic repair. Some use epoxy primer, that's OK too especially on a cosmetic repair. For a cosmetic repair, I try and get the weld as smooth and without pinholes that I can, even if that takes numerous weld/grind cycles.
You have to do BOTH sides of the weld, not just the side you see. How you do that requires some ingenuity sometimes. I've coated the inside of my new heater channels before installation by sloshing paint inside them before welding them in, then using a cheap bore camera to look at the HAZ of the welds and then painting over the top of them to try to seal it from the atmosphere. You just have to try and do something!
The important thing is that you seal the weld area after welding. Rust has to have water and air to work. Water has a small amount of oxygen dissolved in it, so steel can still rust in the total absence of "air". So seal any exposed steel to slow but never eliminate the rust process. If you do a good job on sealing the steel, the rusting will be at microscopic levels and not cause any issue with paint interactions. If you are lazy or sloppy then the result will be bad.
The Titanic sits at the bottom of a cold salty ocean. It has relatively minimal rust given how long it has been exposed to water. Even in cold water there is still some oxygen, but not enough for the rust process to completely destroy the steel.
These days of course cars come with steel that has some sort of galvanised base. New cars do not rust like the cars that I was bought up with from the '60's which were rusting on the dealership lot! VW tried dipping our cars, but this did little to seal folded seams.
The companies pedalling weld through primer are out to make a dollar. There may be evidence that will satisfy my skepticism, but I haven't seen it yet. If someone has it, then I'm happy to be educated.
Well that's a few cents worth and hope it partly explains my position.
And yes I write a lot. It's in the nature of my profession. |
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Lind wrote: |
Have you considered simply starting with a nicer bus? I don't know what your skills are, but the race is easier if you can see the finish line. If you are not a runner, don't start off doing a marathon. |
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