This comes from this web page: http://exp-aircraft.com/library/alexande/painting.html
Since painting aluminum is a common event in planes, I searched for "painting a plane." This is, in part, copied and pasted from the above web page. I guess it depends how involved you want or need to get.
PREPARATION OF SURFACES
Aluminum
Aluminum surfaces are treated differently depending upon whether the metal is new or used. Paint must be able to "grip" or adhere to the surface onto which it is applied. Most aluminum surfaces have a layer of pure aluminum on the surface called alclad that protects the metal from corrosion. It is very smooth and not favorable to paint adhesion. Therefore the surface must be adequately prepared by cleaning and slightly roughening to guarantee primer adhesion. This is accomplished by using a conversion coating such as alodine. This chemical process creates a ceramic layer over the aluminum that coats the surface and provides tooth adhesion. Used aluminum must have any primers, paints, or corrosion removed. Paint strippers are used to remove old paint. After stripping old paint the corrosion should be completely eliminated. Use fine sandpaper, Scotch Brite pads, or aluminum wool. Never use steel wool or a steel brush. After the corrosion is removed the old aluminum should be acid etched. This is simply a process of washing the aluminum with a product such as Poly Fiber's E-2310 Acid Etch diluted with water. An acid etch removes oil and light corrosion while etching or roughening the surface to provide a firm primer bond. The part is then thoroughly rinsed. Next wash the surface with E-2300 Conversion Coating that inhibits corrosion and further enhances primer adhesion. After this step the part is rinsed and allowed to completely dry. Once again, new aluminum surfaces need only be treated with a conversion coating.
After the aluminum (new or old) has been properly cleaned and treated, it is then primed. I would recommend using a two-part epoxy primer. An epoxy primer will insure corrosion protection and also provide a bonding surface for most topcoat paints. Very often, polyurethane topcoats will lift or wrinkle primers other than epoxies much as a paint stripper would do. A primer is necessary to provide a bond between the metal and the final topcoat paint. The primer coat should be applied according to the manufacturers directions. Usually, two light coats will be applied. Heavy coats should be avoided.
TOPCOAT PAINTS
You have a choice of the type of topcoat paint along with a large number of brand names. Enamel is a paint that is commonly used on aircraft surfaces. These paints are sprayed over epoxy primer after being thinned to proper consistency using enamel thinners. A light, mist coat is first sprayed on and allowed to dry for a few minutes until it is tacky to the touch. This is then followed by a full coat of enamel. One full coat may be sufficient or another may be sprayed if desired. The use of enamel is not as popular as it was in the past.
A second type of topcoat paint is acrylic lacquer. This paint has a low solid content that makes it more difficult to apply. Acrylic lacquer should be thinned using the proper thinner and then a very light tack coat applied. An additional 4-5 cross coats of paint will then have to be applied allowing about 30 minutes drying time between coats. (By the way, a cross-coat is defined as moving the spray gun north and south followed by east and west: one cross coat).
Polyurethane paint is probably the most popular choice for a topcoat today. It is very durable and provides a high gloss finish. It is also chemically resistant. These paints have a high solid content and they cure very slowly which means they continue to flow out for a long period of time. This flowing out process forms a very flat surface that gives the surface a high gloss look. Polyurethane enamels are mixed with a catalyst prior to use. They are then reduced to proper viscosity for spraying. A very light tack coat is first applied followed by one or two full coats. One problem inherent in polyurethanes is the thickness of the film applied. If the paint is applied too thick it may tend to crack over a period of time. This is especially true when applied over fabric. The fabric on an airplane will flex and move during flight. This movement coupled with the thickness of polyurethane paint can present a problem. Polyurethane paints designed for fabric airplanes are manufactured and should be used when painting over polyester fabrics.
The one major problem encountered when using polyurethane paints is its toxicity. Breathing the spray mist from polyurethanes may cause severe sickness or even death. With this in mind, you must use a forced air breathing system such as the HobbyAir system. You should also protect your skin and eyes.
