Stripping the Paint

Introduction

Stripping the paint off of your plane can be a time consuming process. Why do you think it costs a minimum of $12,000 (2007 dollars) to have your plane painted? There are two basic methods for stripping and several variations for each. Some information is provided for all of these methods, but until someone actually goes down that path and shares their experience here, details will have to wait.

Chemical vs. Mechanical Stripping

The two basic stripping processes are chemical and mechanical. Chemical stripping is the application of a chemical to the surface of the paint. This chemical works it way into the paint and primer and causes swelling. This swelling usually causes the paint to detach from the underlying surface. Mechanical stripping is an abrasive process.

The basic chemical stripper for who knows how long is based on an industrial solvent called methylene chloride. Methylene chloride will burn your skin and is a known carcinogen. For that reason, safer but often less effective alternatives have been developed.

Chemical Strippers

Methylene chloride can be purchased at most stores that sell paint. Wal-Mart, Home Depot, Lowes, and Ace all sell the stuff. Methylene chloride-based strippers come in different grades. The more expensive the product, the higher the concentration (usually) of methylene chloride and the faster and better it works. The cost of the product can also be an indicator of the quality of the carrier (the gel). Since methylene chloride readily evaporates, the quality of the carrier is important.

Personal protection for methylene chloride requires chemically resistant gloves, other skin protection, chemical goggles, and a respirator. If you choose not to use a respirator, you will need extremely good ventilation. Goggles may not be necessary if you brush instead of spray, but there's always a chance of splashing or rubbing it into your eyes.

Safer alternatives to methylene chloride now exist. Some people swear by them and others think they are less effective. The most common one is the generic citrus strip, but Jasco makes a product that looks like green slime. These alternatives are usually more expensive, though. If using chemical strippers, you will have to balance safety with the size of your wallet.

Chemical strippers should not be used on fiberglass or other composite parts. The same action that causes the paint to swell will damage the matrix material in the composite either weakening the matrix and/or causing delamination.

Mechanical Stripping

Mechanical stripping can be used to strip the entire aircraft or as a finishing step. For most light general aviation aircraft, chemical stripping is used for the majority of the work. Mechanical stripping can be broken down into two basic processes, blasting and sanding.

First and foremost, blasting uses abrasive particles under pressure and can easily damage thin aluminum either through being overly abrasive, causing heat buildup (oil canning), or both. Second, you will probably not use a blasting process yourself. This usually requires industrial equipment. Some local car shops may have this equipment. If considering blasting, safer (not necessarily safe) methods include soda, walnut shell, and plastic media blasting. Plastic media blasting is now being used in military depot work and is supposed to be milspec'd down to 0.016 aluminum. However, some have indicated that plastic media should not be used on aluminum this thin. If considering this route, perhaps you should have the shop test their method on some scrap of the same gauge and alloy of the pieces you need stripped. See the maintenance manual for this information. Soda blasting can be messy and can get into every nook and cranny, but the equipment is typically portable. Like plastic media, some claim that it will damage thin aluminum.

The other basic form of mechanical stripping is sanding. This usually involves a dual-action or random orbit sander with different grits. However, another common method for detail work is to use Scotch Brite wheels on a die or angle grinder.

Mechanical stripping should be the primary method for composite parts.