Corrosion Removers
Airplanes spend a lot of time in moisture when they're up in the air, and if you have humid conditions around your hangar, they can stay in damp air virtually all the time. You're going to get small areas of corrosion periodically. After treating with a degreaser, you'll apply these acid-based removers and then scrub away all signs of oxidation. Most of these removers are designed to make the aluminum on your plane's exterior brighter when you're done cleaning.
Pre-Paint Coatings
If you're adding a coat of paint, sometimes you're covering up corrosion that's too small to see with the naked eye. Under that coat of paint, the corrosion can continue to grow and then come up through the new paint. Conversion coatings come in powder and liquid form for you to treat the surface of your plane before adding the next coat of paint.
Fuel Line Solvents
These chemicals will wash any sulfates and salts out of your gas line, which will keep your fuel system from developing carbon-based corrosion. This sort of wear in the middle of the inner workings of your airplane's engine will be expensive to repair. Using these sorts of solvents will keep you from having to make those repairs as often -- if at all.
Surface Strippers
If you're repainting, these chemicals will remove existing paint to help you get back down to the original metal instead of painting over old layers. Some of these are based in benzyl alcohol and others are based in peroxide. Alcohol-based strippers are more useful with epoxy resins; peroxide-based strippers are recommended for planes that have magnesium surfaces.