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There are several questions about livery changes and livery in general on this website. Yet, I fail to find information about paint removal.

As a routine maintenance for an airframe that can live for up to 30 years, livery is redone several time as explained here. When changing painting, it should be preferable to remove the old one (I'm mostly thinking about weight as a big airliners has a lot a surface to paint). Moreover, I imagine that for military aircraft changing their operation theater, paint must be redone to adapt camouflage, and thus accumulating many layers of paint may have consequences.

Given material and other aviation-specific constraints, I also imagine there are special techniques to handle any intervention on the airframe.

Is this paint removal done and if so, how?

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  • $\begingroup$ I know tanks and other ground vehicles get new camo jobs, but I don't think aircraft do, do they? The air is the same color in either case. $\endgroup$ – Hosch250 Sep 11 at 17:17
  • $\begingroup$ Tangentially related: aviation.stackexchange.com/questions/14500/… $\endgroup$ – user3067860 Sep 11 at 18:38
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    $\begingroup$ @Hosch250, the air may be the same color, but the ground isn't, and military airplanes tend to spend most of their time on or very close to the ground. $\endgroup$ – Mark Sep 11 at 22:36
  • $\begingroup$ I think they typically land pretty far behind the fighting line--some planes are only based out of the US midwest and do round-trips--notably spy and bombers. They are painted to provide camouflage/mind tricks in combat (which way is the plane actually oriented, am I looking at the top or bottom) etc. Maybe I'll post my own question about this, though. $\endgroup$ – Hosch250 Sep 12 at 17:53
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    $\begingroup$ @Hosch250 The US midwest is, proportionally, only a very small part of the world. $\endgroup$ – Lightness Races with Monica Sep 13 at 11:17
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Paint stripper. Lots of paint stripper. (originally I said thinner, but I have been corrected, it's more accurately called stripper)

Seriously though, it's actually not too different to other things that you paint. You need to spray on paint stripper. But, just like when painting the aircraft, it's imperative that you cover up all the delicate systems on the aircraft fuselage.

See here:

Also, I think it would be rare to paint a new livery over and existing one without first removing the old paint (maybe only if you were just changing small details), because covering an aircraft in paint weighs A LOT. For a 747 or 777 sized aircraft the paint job can weigh over 1000lbs

Carrying that around costs fuel and fuel costs a lot!

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    $\begingroup$ Welcome to Aviation.SE! Nice first contribution, I hope you stick around. $\endgroup$ – AEhere supports Monica Sep 11 at 8:09
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    $\begingroup$ When my plane was repainted in fall in 2018, paint stripper was used. Hydrogen peroxide based, it took everything off. crossroadsfencing.com/airplane/painting%20pics/IMG_0200.JPG After sitting overnight, the plane is rinsed and the wastewater collected in barrels to be shipped off and processed somehow. Some areas needed a 2nd application to get down to bare aluminum crossroadsfencing.com/airplane/painting%20pics/IMG_0202.JPG $\endgroup$ – CrossRoads Sep 11 at 12:13
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    $\begingroup$ Paint thinner is mineral spirits (Stoddard solvent) which may have been washed, i.e. recycled. Paint stripper is an organic solvent mixed with wax to slow evaporation; the solvent penetrates the paint and causes bubbling as it evaporates lifting the paint. Methylene chloride and NMP are common. The stripper in the video is a combination of solvent and caustic compounds such as lye that actually dissolve cured paint. You won't find them at the local hardware store because they also dissolve the lignum in wood, but they are sold to shipyards, and I assume, aircraft painters. $\endgroup$ – Matthew Gauthier Sep 11 at 15:37
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    $\begingroup$ If I had to guess the stuff they are using in that video is called, "Aircraft Stripper". IN cycling, if you paint your frame, you can remove baked on coatings with it as well. For a consumer, you can buy small jugs, of it. It's basically a corrosive chemical that bubbles the paint off. Example: kleanstrip.com/product/aircraft-paint-remover $\endgroup$ – knocked loose Sep 11 at 19:04
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    $\begingroup$ Stoddard solvent is a mild case of a paint thinner. More serious ones: Acetone, Nitrocellulose thinner, Methyl-Ethyl Ketone (MEK), Stabilised Tetrahydrofurane (THF).... $\endgroup$ – rackandboneman Sep 11 at 20:13
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In addition to the chemical method in Simon's answer, there are mechanical methods, like bead blasting. This method was introduced in the 80s by airforces concerned with the volume of chemical waste generated by their maintenance facilities.

It essentially consists of using compressed air to project fine plastic particles against the painted part at high speed. These abrade the paint away mechanically and can be recycled a few times before they break down too much and become ineffective. Glass particles can also be used for more heavy duty blasting, but these need more careful procedures to avoid damaging the substrate, since they are much harder than plastic.

Abrasive blasting not only removes paint, but also dirt, corrosion and even anodic coatings, with enough passes.

Whether it has any advantages over chemical stripping, depends on the specific case. Industry regulations change across time and space, and waste plastic dust might be more problematic than waste chemicals in some places, but not others. Also, the size of the parts to be stripped and the kind of training required for the operators play a significant role in choosing one method over another.

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    $\begingroup$ Baking Soda blasting is another method for mechanical removal. youtube.com/watch?v=lub0D1pX_xo $\endgroup$ – CrossRoads Sep 11 at 12:02
  • $\begingroup$ @CrossRoads same principle, different blasting agent. $\endgroup$ – jwenting Sep 12 at 4:38
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Not to be a smart-ass, but I think the correct answer is "in accordance with the airframe manufacturer's instructions."

Aircraft are generally given a corrosion protective layer (or passivated) at the time of manufacture that usually gives them a green color before they are painted. For this reason, unpainted planes are sometimes called "green" planes. Historically the treatment was usually a zinc chromate primer, but that is highly toxic and I doubt anybody still uses it on new planes. I suspect some of the more modern treatments add green pigments just to give the green planes the expected look, but I don't actually know that.

Following manufacturer instruction on whether and how to use chemical strippers or mechanical removal of paint is important to not damage the protective layer in ways not expected by the manufacturer. Some treatments require parts to be dipped in a chemical bath before assembly, so if you remove or damage that treatment layer, you're not likely to be able to restore the corrosion protection to an as-new status. If you remove the protection and replace it with your own in a way not specifically approved by the manufacturer, your plane no longer is in full compliance with the type certificate and you've become something of a test pilot.

TL;DR: Don't do stuff to planes that isn't approved by the manufacturer or a supplemental type certificate applicable to your specific plane.

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    $\begingroup$ Stripped planes are taken down to bare aluminim. The AL is then washed, acid etched (something like a mild vinegar), alodyne applied, then primer (the green color), then paint. The stripper doesn't know to stop at the primer level. This was mine after the alodyne stage, before primer crossroadsfencing.com/airplane/painting%20pics/IMG_0311.JPG $\endgroup$ – CrossRoads Sep 12 at 11:59
  • $\begingroup$ @CrossRoads Reminds me of a DeLorean :-) but I'm afraid it lacks the Flux Capacitor. $\endgroup$ – PerlDuck Sep 12 at 17:46
  • $\begingroup$ Well, that and stainless steel :) $\endgroup$ – CrossRoads Sep 12 at 18:52
  • $\begingroup$ Yes, @CrossRoads, but the look is awesome! $\endgroup$ – PerlDuck Sep 12 at 18:57
  • $\begingroup$ The green layer is just a temporary protection that gets stripped before the aircraft is painted. $\endgroup$ – fooot Sep 16 at 15:20
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There are other methods in addition to the chemical and mechanical ones already mentioned in other answers. In some cases, paint is removed from aircraft using a laser.

Here's a video I found from the US Air Force that demonstrates the process:

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    $\begingroup$ F16, 25 hours for 2 robots. C130, 75 hours for 4 robots. Bet a Cessna would be pricey, if one could get time at an AF base to have it done. $\endgroup$ – CrossRoads Sep 12 at 16:14

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