Is the old paint removed before applying a new one?

Question

I've heard that paint on large airplanes weigh 250+ kg.

When an aircraft gets a new owner, do they remove the paint that was previously on or simply paint over it?

If it is removed, how is it removed? What is the correct procedure for painting/repainting an aircraft?

Answer 1

Yes, paint imposes a significant weight penalty on larger aircraft. On commercial airliners, that weight translates to a reduction in cargo, passenger and fuel carrying capacity, and that means less money to be made on every flight. That is why some airlines have chosen to remove most of the paint and opt for the bare-metal look. However, there are tradeoffs to be considered, such as the fact that bare metal is much more susceptible to corrosion.

These days removing paint from an aircraft is a relatively straightforward proposition if you know what you are doing. There are a number of environmentally-friendly paint stripping chemicals available that when applied to the aircraft surface, cause the paint to bubble and lift off the underlying airframe.

The paint can then be scraped off with plastic tools or removed with a pressure washer, and the stripping chemical is washed off. Other products are then used to clean remaining residue, treat the metal for corrosion protection, prime and paint.

This explanation is intentionally simplistic, but it covers the basics to answer your question. If you want to see the process in action, you might check the many YouTube videos that show time-lapse recordings of aircraft being painted. Personally. I think they are fun to watch. :)

Answer 2

Adding to Juan's answer:

It depends on the new operator (I intentionally didn't say owner). If the new operator is leasing the plane for a short time, they usually just use easily removable decals (which may look ugly after some flying).

Even if the operator doesn't change, the plane is repainted usually once every 5 to 8 years as this KLM blog explains. In this case the old layer is indeed removed.

Sanding and stripping

An aircraft can be disrobed of its old paint coat in a number of ways. A Fokker is sanded by hand with a sander. A Boeing or Airbus is partially sanded, partially stripped. Stripping is carried out using a liquid which, at 25°C, can strip an aircraft of all its paint in 24 hours. Once all the old paint has been removed, the primer is sprayed onto the aircraft. It takes around six hours for each layer to dry.

Answer 3

If you're referring to airliners, the paint indeed has a significant effect on the aircraft weight and more importantly center of gravity. Airliners are mostly sold on plain white, with all but mandatory markings removed. When a new paint-over is done, the aircraft must be weighed to determine the new weight and CoG. Small partial paintings can be made without the need to weigh the aircraft, but unfortunately I don't know what are the limitations.
Aircraft must also be weighed regularly every 3-5 years, even if no painting or other modifications are made.