Numbers have etched the aluminum?

[Aubiexx]

I am preparing to polish our 70 overlander and removed the plastic/vinyl part of the WB numbers with airplane paint stripper, however it appears that the adhesive used for the numbers has somehow etched into the aluminum? Is that possible?

If anyone has had successful experience with this I would love to know. Thank you in advance

[InsideOut]

Yes, it unfortunately is possible. Sometimes this can be removed by polishing...but oftentimes they can still be seen. If you are going to replace the numbers, the new numbers can help hide the "ghosts" too. If you aren't a member and want to become one you can also check with the main office to see it the same number is available for you to use.

Shari

[Bill M.]

Yeah, the numbers change the color of the aluminum. It can be polished out with a big cyclone polisher, but then do you really want to pay 10 grand to do the whole trailer or to have a bright spot at each end? I cleaned mine off best I could and put the new numbers on. Obvious that there were numbers before. Have you tried taking the numbers off yet? That can be a daunting job in itself.

[DougZ]

You may be able to get rid of the ghosts if you sand that whole section down with 1000 or 2000 grit wet sandpaper and then polishing. I have gotten water etched spots out of aluminum sheets this way at work.

[Janie Q]

I took a heat gun and put it on low, then moved the gun slowly around one number at a time.. do not keep the gun in one spot.. peeled off in a matter of seconds..

Jane

[Aubiexx]

Originally Posted by DougZ

You may be able to get rid of the ghosts if you sand that whole section down with 1000 or 2000 grit wet sandpaper and then polishing. I have gotten water etched spots out of aluminum sheets this way at work.

Thank you for the insight. I will get on that this weekend and post my results, hope to have before/after pics.

[InsideOut]

Originally Posted by DougZ

...if you sand that whole section down with 1000 or 2000 grit wet sandpaper...

Originally Posted by Aubiexx

Thank you for the insight. I will get on that this weekend and post my results, hope to have before/after pics.

Careful you don't sand through the Alclad...that is not repairable - w/o replacing the skin.

Shari

[ALANSD]

question on the sanding- I am doing that to remove some corrosion. Use a sanding block, or hand sand or? Thanks
I have 600 grit up to 1500 to use for wet sanding as needed.

[eubank]

Originally Posted by InsideOut

... If you aren't a member and want to become one you can also check with the main office to see it the same number is available for you to use. Shari

Exactly what we did! A perfect way to hide the etching -- and we get to enjoy our membership to boot!


Lynn

[DougZ]

Originally Posted by InsideOut

Careful you don't sand through the Alclad...that is not repairable - w/o replacing the skin.

Shari

Shari, I don't pretend to be an expert on the finish, but I think the only place that any Chromate may be left on this vintage AS might be under the numbers. The rest will probably be weathered away. The finishes on aluminum are fragile to say the least. Anodized aluminum can be compromized in just a couple of years in the right atmosphere. I'm sure there are experts that will weigh in.








doug

[Nuvite-F]

Originally Posted by DougZ

Shari, I don't pretend to be an expert on the finish, but I think the only place that any Chromate may be left on this vintage AS might be under the numbers. The rest will probably be weathered away. The finishes on aluminum are fragile to say the least. Anodized aluminum can be compromized in just a couple of years in the right atmosphere. I'm sure there are experts that will weigh in.

Whoa! Airstream trailers were never anodized except for Wally's gold anodized trailer, which is now badly faded and not repairable except to replace the skin.

When Sheri referred to sanding through the Alclad, she was referring to the fact that prior to the early 80's the Airstream skin was made of Alclad aircraft-grade aluminum, consisting of a sheet of high strength alloy (2024-T3, I believe) with a .005 inch thick layer of pure aluminum bonded on the outer surface. This thin layer of pure aluminum is more corrosion resistant than the alloy underneath, and takes a beautiful polish. But you can polish right through it, if you're not careful with coarse abrasives.
.

[Wabbiteer]

I used an aerosol spray-on gasket remover - melted the numbers away, now have perfect aluminum ONLY where the numbers used to be

[DougZ]

Originally Posted by Nuvite-F

Whoa! Airstream trailers were never anodized except for Wally's gold anodized trailer, which is now badly faded and not repairable except to replace the skin.

When Sheri referred to sanding through the Alclad, she was referring to the fact that prior to the early 80's the Airstream skin was made of Alclad aircraft-grade aluminum, consisting of a sheet of high strength alloy (2024-T3, I believe) with a .005 inch thick layer of pure aluminum bonded on the outer surface. This thin layer of pure aluminum is more corrosion resistant than the alloy underneath, and takes a beautiful polish. But you can polish right through it, if you're not careful with coarse abrasives.
.

I wasn't trying to say that AS are or were anodized. I was using anodize as the ultimate protection of aluminum and anyone who owns a boat knows even anodize doesn't hold up against salt or other environmental attacks. 40 years of sun, snow, washing, salt or what ever are going to take their toll on the finish. According to Wikipedia Alclad is: "a heat-treated aluminum, copper, manganese, magnesium alloy that has the corrosion resistance of pure metal at the surface and the strength of the strong alloy underneath." My theory is that if the Alclad was still intact, there would be no evidence of the numbers once they were removed. Remember - this is just my theory, so don't go hoggin' into the aluminum with a grinder.

[Nuvite-F]

Originally Posted by DougZ

My theory is that if the Alclad was still intact, there would be no evidence of the numbers once they were removed. Remember - this is just my theory, so don't go hoggin' into the aluminum with a grinder.

No, it's probably intact. Pure aluminum is more corrosion resistant than the underlying alloy, but not infinitely so. Most old trailers have ghosts of the old numbers on them. The other thing you will discover when you start polishing is that each sheet of aluminum is a little different, and at least on the one trailer I polished, the compound curved panels of the end shells seem to have "stretch marks" that are hard to polish out.

Good luck!
.

[DougZ]

Originally Posted by Nuvite-F

No, it's probably intact. Pure aluminum is more corrosion resistant than the underlying alloy, but not infinitely so. Most old trailers have ghosts of the old numbers on them. The other thing you will discover when you start polishing is that each sheet of aluminum is a little different, and at least on the one trailer I polished, the compound curved panels of the end shells seem to have "stretch marks" that are hard to polish out.

Good luck!
.

What do your stretch marks look like? I looked on mine (which has not been buffed) and couldn't find anything. This aluminum thing is getting complicated.

[Frank's Trailer Works]

I think this may have already been said, but the numbers do not cause any damage to the skin. What does cause the issues is the area around the numbers that actually is exposed. The numbers, when stripped, do not remain, the clean perfect aluminum is exposed. You see the oxidation around the numbers. The more exposer, the deeper the ghost image will be. Sometimes this is impossible to remove and just has to be looked at as history.
Nuvi is very correct about the stretch marks. The seven panel end caps have the least due to less stretch forming required. The five panel end caps will show even more due to each segment being a wider span and having required more tonnage to form it. The modern aluminum used today does not form these stretch marks due to it being a totally different alloy of aluminum (it is the same as license plates are made from) but cannot be polished as Alclad can. Any metal can be polished. Some polish better than others.
I always wonder though, why the center panel on a new Airstream is a totally different color than the rest of the end cap. I asked someone from Colonial this and they kind of side tracked the answer. I assume they did not know either.

[Nuvite-F]

Originally Posted by DougZ

What do your stretch marks look like? I looked on mine (which has not been buffed) and couldn't find anything. This aluminum thing is getting complicated.

The "stretch marks" I mentioned are kinda hard to describe. They don't show up till you start cutting through the oxide. After a couple passes with coarse polish (you will probably find it will take several passes to get through to clean aluminum--at least I did) you will notice thin dark streaks where the oxide is thicker. I suspect this is where the pure aluminum layer stretched out a little thinner when the panel was formed. It's not a problem aside from the fact that those panels will take more polishing to get the oxide off than the other panels. Or you can do like I did and let some of the oxide stay--I didn't want to polish right through the cladding.

And yeah, you're right--"this aluminum thing" is a lot more complicated than most people realize! I found a lot of variation in polishing behavior between one panel and another. It's more of an art than a science.

Dale (Pee Wee) Schwamborn worked for Airstream, and purchased their aluminum for a number of years. He has a lot of good stories to tell about it. I've forgotten the details, but I recall Airstream bought the aluminum they used for single-curved panels from one manufacturer (Reynolds, I think) but the aluminum for the compound-curved end shells from another (Kaiser) because the different brands worked better in those uses. (I may have Reynolds and Kaiser reversed.) Nobody knew why.

The other Pee Wee story is that if you look at the pictures of new 60's Airstreams, they looked like they had been polished. They weren't--that's what the aluminum looked like when it came from the rolling mill.

And therein lies a tale. The quality of the surface finish of the sheet depends on the surface finish of the rollers in the rolling mill. The rolls are reground at frequent intervals and the first batches of aluminum sheet that come off the new rolls are better than later batches.

Aluminum is purchased to a specification, and all the aluminum meets the specification. But Boeing paid extra to get the first batches off new rolls so they had the best surface finish.

But there was one relatively small customer that got their aluminum even before Boeing--Airstream.
.

[Aubiexx]

Attached should be a before pic. I did get a promising amount of the etching to smooth out through compound cut. Will post more later.

Got a little over half of the first cut done this weekend.

[ALANSD]

I have had some success with 1000 grit wet sandpaper, and then brown tripoli. The numbers are almost totally invisible now.