by Tucguy » Thu Oct 09, 2014 1:06 pm
I am an aircraft structural tech. Airplanes are mostly aluminum. This is how the pros do it:The process for painting it: Finish all your shaping, drilling, stretching, etc. Use scotch brite pad on it to lightly roughen the surface. Use aluminum prep and then chromic acid (alodine) very carefully as they are easily absorbed into your skin and liver. they are sprayed or rubbed onto the aluminum. Best method is to emmerse in tanks. It changes the surface color to a light copper in a few minutes. Wash it off with water, being careful to contain the waste. It is hazardous waste, treat is as old oil paint and turn it in to an appropriate agency. It is available from aircraft supply businesses such as Aircraft Spruce. The alodine is called a conversion coating. Most important for aluminum painting process. Primer it with a two part epoxy (Koropon) and then topcoat with a two part epoxy finish. This gives you a very long lasting finish resistant to corrosion. Yes aluminum does corrode, especially when it is in contact with another metal such as steel (screws). You would be using caulk under your trim and under the screws to minimize moisture infiltration and that helps the problem with dissimilar metal corrosion as well. This how we treat aluminum airplanes. This is the same method to paint an aluminum covered trailer as well if you want the best and the longest lasting finish. Every aluminum part on an airplane is treated this way although some are only primed if they are not visible. Best environmental protection is with the topcoat over the primer. Anodization is the other best method of coloring aluminum but is expensive and is more like applying chrome. Big vats of chemicals and electricity.