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Ghost lines from welded patch panels

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#1 ·
First off, this is my first post. figure i should say thanks to all of you since i have been learning so many new things from this site that have made my life a little easier. I am a collision painter. I do all of my own personal bodywork and i have been doing it for a few years. this problem has been bothering me lately though. I am having this issue where all of my patch panels have been welded in on my car. I did the bodywork last winter, sprayed it right after and i noticed the ghost spots once it sat in the sun for a couple days. a block and buff will hide them for a month or so but then they faintly re appear over time. my process was the following:

1) cut filler panels to exact size, same gauge sheet metal as factory panel. stripped paint back ~4" around are to be welded

2) butt welded in place. about 5 tacks spread apart, let panel air cool, then 5 more in between previous, etc. once it looked solid i ground down the welds, used my hand sand blaster gun to clean out the small gaps between the welds, then welded the remaining gaps up. (miller 180 w/ gas)

3) ground down the remaining welds

4) I have done both of these processes on 2 different patch locations on the car. First was a coat of duraglass filler, rage gold, icing. then the other was just rage gold, icing. both areas have the same ghost effect. after i block out each filler i tend to let it sit for an hour or so to make sure its had some time to cure before skimming on the next. all done in 70-80 degree shop temp.

anyone have any ideas what my problem might be? i figured it would be filler shrinking into gaps between welds because thats what the ghost image looks similar to, but i make sure to leave no gaps before filler. nobody else has noticed it but its one of those things that pisses you off to no end. i spent a ton of time blocking, priming, letting everything shrink, flow coating, buffing to get a super straight/super smooth panel then to have a ghost line appear where my welds are :pain: I am currently in the process of respraying the car a different color and it got to the point where i stripped the doors down just to make sure all of the prior metal work looked proper since i have learned much more about metal work over the last year than i did when i started working on this car last winter
 
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#3 ·
mitmaks said:
what is your process after your filler work is done, what primer are you using, how long do you wait for it to cure, etc?
ppg k38. medium coats, 20 minutes flash time between, 2-3 coats. shop temp is roughly 70ish degrees always (during winter). sits overnight, knock the surface down with 180 and let sit another day to allow solvent to escape. finish blocking with 180, re-prime. let sit overnight, knock the surface with 320 then i let it sit like that until im ready for final block/paint, usually a few days minimum since i work on my personal stuff whenever i have free time. no issues with sand scratches, feather edges or anything else. just faint ghost spots where the welds are. if the panels were not blocked and buffed you probably wouldn't even notice, but on a cut and buffed panel it stands out to me
 
#6 ·
What kind of car and where-area wise- are these patches located? I am thinking the metal may be shrinking-expanding at different rates than the stock metal. Cold roll metal is supposed to have a "grain" to it and may be the problem. Thickness and tensile strength? I am not an expert by any means, I have been to a few classes by Winfield, and he has mentioned that these things can make a difference. Personally, I would think a skim coat and a few coats of primer would have hid this, but like I say, I am no expert.
 
#7 ·
expansion from heat is the only thing i can logically think of causing the issue. car is an 04 vw gti. I actually cut my patch panels from a spare vw oem hood that i had at the shop so i know its all the same material. and for expansion i figured the patch that has the coat of duraglass over it wouldn't be an issue but it didn't make a difference.

Not my car (no pics of when i did mine), but i did the same job. shaved the door handle pockets. also shaved the handle completely on the hatch but that was just a 3"x5" rectangle opening

 
#11 ·
Your problem is that you’re using a butt weld. They have their uses such as doglegs and pillar posts, but are not the best choice all around. Because metal flexes it tends to bend at the weakest joints. I use an overlap weld without flanging. It provides a stronger weld hold without flex fatigue associated as evidenced with a butt weld.

I’ve provided two photos of an Acura I sectioned a quarter panel on last week.

 
#12 ·
302 Z28 said:
Dang near every patch panel installed has been MIG welded in place. If that is the problem then there are hundreds of thousands of cars running around with this problem. Your problem is not caused by MIG welding :rolleyes: .

Vince
All MIG welds are not the same........a lot depends on the quality of the wire, the heat settings, etc.
 
#14 ·
I've heard of this complaint from other people before. From what I've heard it's usually appears in the sun when it get hot and the weld and the panel expand at different rates. I hope my current project doesn't have this problem, but I'm doing the body work just like you describe.

My friend replaced the rear quarters on his '70 Firebird and has the same problem.
 
#15 ·
cjperotti said:
Your problem is that you’re using a butt weld. They have their uses such as doglegs and pillar posts, but are not the best choice all around. Because metal flexes it tends to bend at the weakest joints. I use an overlap weld without flanging. It provides a stronger weld hold without flex fatigue associated as evidenced with a butt weld.

I’ve provided two photos of an Acura I sectioned a quarter panel on last week.

for me to overlap a patch panel for the door handle it would have to overlap on the outside of the door, not the backside. not sure which way you overlap. the pocket has to stay there, cant be cut out because the inner handle/latch assembly is built to work with the pocket in the sheet metal. if i overlapped on the outside i beleive the area would be too high for me to be able to make the handle work proerly. the patch is welded in flush with the door skin but i also drilled some holes in the pocket from inside the door so shoot rust fighter in there for protection.
 
#20 ·
You will see butt welding on a lot of forums that doesn’t make it the best recommended weld available. It is the stupidest weld to use on any structural repair or replacement panel period.

ASI and most manufacturers don’t recommend butt welding replacement panels and for a reason. If you want to butt weld do so at your own risk.
 
#21 ·
butt weld and tig . he's just trying to shave door handles. just what structure is he dealing with. and yes mig welds are harder. most times when they ghost it's because too much weld was left .
 
#23 ·
swvalcon said:
I've been doing this for 40 ys and the only time I've seen this happen is back in the days when we used bass and a torch. You didn't use a flux coated wire by any chance did you.
no flux core wire. welder is the same setup the guys use for all the shop collision work. theres not a lot of butt welding on there side that i see but we have never had anything come back because of ghosting issues. like i said if the panel had a factory-ish peel to it, it would hardly be noticeable. but when the panel is flat it stands out.
 
#24 · (Edited)
i thought this might be interesting to the debate here. i shortened it to the relevent parts:


http://en.allexperts.com/q/Auto-body-repair-2036/Replacing-Cab-extension-panels-3.htm




Butt welding is no way to install a panel, it goes against every rule of modern panel sectioning as outlined by all the manufactures, and I-car. Even if you section it through the window frames, butt welding is an unsafe procedure. (snip)

If you don't mind I'd like to ask you to elaborate further on why lap welding vs butt welding replacement panels. I see it done all the time on shows like Overhaulin, American Hot Rod, and in how-to mag articles and I see them lap some too.


If you do this with 2 flat pieces of sheet, then dress the weld down, the weld is easily broken or torn apart when bent. That is why the flanger is best. The metal seam should be completely welded together, with 1/2 inch seam welds. I also will do plug welds every couple of inches, that is just a 5/16 hole drilled into the new panel, abut 1/8 or so below the lip. This adds extra strength. The reason you see guys butt welding on cars on TV shows is just for speed, or for show vehicles that the guys don't want any seams showing in the trunk, or pure ignorance of what heat does to sheet metal. Also, sometimes it's impossible, or impractical, to flange the existing panel to accept a patch. The thinking is, that the lap is a place for rust to start, which is true. I look at it from a stand point of strength, because I'm a collision repair expert. I'll sacrifice a little longevity to gain strength. The vehicle surviving an accident in the area I repaired is incredibly important to me, from a personal and legal stand point. If I butt welded a panel in, and another vehicle blasts through the panel like it isn't there, then I jeopardized that person's safety. That is why I don't like butt welds, the heat permanently weakens the metal, no matter how much skill was involved in the repair. According to I-car, even my flanging technique isn't acceptable on rocker splices, sail panel splices, and splicing a panel through the windows. Much less a butt weld! I-car says to fit the pieces up, and trim them like you are going to do a butt weld, but leave a 1/16 gap between the panels. Then, you take a 2 inch wide piece of sheet metal from the old panel, fit it up and under the existing panel. Then you plug weld it into place, leaving 1 inch sticking down that the new panel laps on to. Then, you drill 5/ 16 plug weld holes into the new panel, every 1-1/2 inches. The new panel is fitted, and the panel is attached at the seam with plug welds. Then, the seam is closed with half inch stitch welds. It's incredibly strong, but prone to catching water. So, it needs undercoated with paraffin based under coat. Sound familiar? But, when I send a young woman and her little children down the drive, I know that if they get hit, my repair will protect them, and the car will react in the way the manufacturer intended.


William Forster
Expertise
22 year veteran, 2 years of vocational training. A.S.E. certified Master collision repair/refinish technician. I-CAR certified. 17 yrs. GM experience. I can answer most questions related to automotive body repairs, ranging from small scratch repairs all the way up to the most extensive collision repairs.
 
#25 ·
spitfire481 said:
the pocket has to stay there, cant be cut out because the inner handle/latch assembly is built to work with the pocket in the sheet metal. if i overlapped on the outside i beleive the area would be too high for me to be able to make the handle work proerly. the patch is welded in flush with the door skin but i also drilled some holes in the pocket from inside the door so shoot rust fighter in there for protection.
He didnt remove the pocket he shaved so the "structural integrity" is still there.
 
#26 ·
Underground said:
He didnt remove the pocket he shaved so the "structural integrity" is still there.
correct. you cant remove the cup section because the inner working all function around that. so my patch panel was just to cover the cup section and make it level with the rest of the door. factory door handle area for reference:



here is an end result for reference:

 
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