Epoxy over galvanized steel? Flux around welds?

theastronaut

theastronaut

Promoted Users
I bought a new tailgate from Dennis Carpenter for the F100 I'm restoring. It's made from galvanized sheet, and there seems to be some kind of sticky/waxy flux(?) around the tailgate end cap welds. What do I need to do to prep the metal and clean whatever is off of the end caps to ensure proper adhesion? There is also a zinc? coated piece welded in for the tailgate supports; should I blast the coating off of those or are they ok with just scuffing before epoxy? Is ospho followed by a rinse while its still wet a good idea on galvanized steel?

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Sanded galvanized is just fine, but coatings should be removed. I'd try solvent based wax and grease remover on the waxy stuff. You don't need to use ospho on the galvanized, imo, just 150 or coarser.
 
Solvent based W&G will take it off but the galvanized coating is darkened/etched underneath, I was thinking it may be acidic and should be neutralized?



Left half cleaned with W&G remover.

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Hard to say from here, but if you think it's some kind of acidic residue, ospho'ing it and washing it very well might be a good plan. I'd wait to hear from some others on this one. I might continue cleaning it with water based like #700 and then blast the ends, since we don't use ospho at all here.
 
I called Carpenter's tech line and they did confirm that they use flux but had no details available on what type it is or if it's acidic. It's in between the layers so I'm worried it'll work it's way out later. I know Ospho isn't recommended but have seen that it can work if properly rinsed off while it's still wet, but I'm open to other options too.
 
I think ospho might be fine. Afterward you might also want to seal up all the holes and slosh some epoxy around the inside.

@Barry , what do you say?
 
That looks like galvanealed not galvanized. Galvanized looks patchy, galvanealed is uniform. Galvanealed is paintable. New cars use it on steel body panels. 80 to 180 on the DA to get some scratches on it and epoxy. I wouldn't muck about with ospho on it as there is no need.

As for the flux and the Tech Line I would have no earthly idea what they would use flux for??? Sounds like a load of BS they were feeding you. Chances are those panels were made by a third party and they have no clue what they are talking about. It's Cavity Wax.The only type of flux they would use is flux core wire. Those are plug welds not spot welds right? Can't see them welding that with flux core.
Discoloration is the galvanealed discoloring from the heat of welding. Waxy stuff is some type of cavity wax. For rust prevention while the part waits to be sold. Same reason they used the galvanealed steel. It's definitely not a flux.
Clean it with solvent based W&G remover and sand exposed areas with 80 up to 180. Plastic scrub brush works well with a solvent based W&G remover on those areas to get it off.
 
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After following the fantastic work you have done on your F100 in a previous thread I know your opinion on the quality of the tailgate will be well informed. How does it compare to an original? The same gage metal? Will it take the weight when down/extended? Straight and with body lines that match in the right places?
I‘m working on a 72 F100 and not sure if I want to keep-after trying to get my original back in perfect shape, or just throw in the towel and buy a repro...
thanks
 
Chris_Hamilton said:
That looks like galvanealed not galvanized. Galvanized looks patchy, galvanealed is uniform. Galvanealed is paintable. New cars use it on steel body panels. 80 to 180 on the DA to get some scratches on it and epoxy. I wouldn't muck about with ospho on it as there is no need.

As for the flux and the Tech Line I would have no earthly idea what they would use flux for??? Sounds like a load of BS they were feeding you. Chances are those panels were made by a third party and they have no clue what they are talking about. It's Cavity Wax.The only type of flux they would use is flux core wire. Those are plug welds not spot welds right? Can't see them welding that with flux core.
Discoloration is the galvanealed discoloring from the heat of welding. Waxy stuff is some type of cavity wax. For rust prevention while the part waits to be sold. Same reason they used the galvanealed steel. It's definitely not a flux.
Clean it with solvent based W&G remover and sand exposed areas with 80 up to 180. Plastic scrub brush works well with a solvent based W&G remover on those areas to get it off.
Click to expand...

I believe you're right about it being galvanealed. They do supposedly make the panels themselves, using original Ford dies. The discoloration is wherever the coating is, not just around the heat affected areas from welding- leading me to believe that it's possibly acidic and not cavity wax. I did describe it as "waxy", which wasn't the best choice of words. It's built up similarly to cavity wax but is more chalky than wax and W&G remover doesn't take it off nearly as easily as it does wax. I did try a degreaser, and hot water with blue Dawn, and neither affected it too much so I don't think it's oil/wax based.


MAKZ06 said:
After following the fantastic work you have done on your F100 in a previous thread I know your opinion on the quality of the tailgate will be well informed. How does it compare to an original? The same gage metal? Will it take the weight when down/extended? Straight and with body lines that match in the right places?
I‘m working on a 72 F100 and not sure if I want to keep-after trying to get my original back in perfect shape, or just throw in the towel and buy a repro...
thanks
Click to expand...

Without fitting it yet I'll say that the tailgate is pretty good overall. The center lettering and beading is stamped very well. Some of the edges are a bit rough but I don't have a factory tailgate in bare metal to compare to. I'll post full details in the build thread once I fit it to the bed.
 
Looks like galvanealed to me. Other terms I've heard it referred to are "paint grip" and "zinc grip". It is made to be painted and holds a variety of paint types well. The epoxy after prep will be best. The white substance around the weld is the burned off zinc, clean that well.
 
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