I found a way to spray paint small parts inside my garage without getting overspray onto everything in sight. That makes me very very happy because I had been very very worried that I would make a huge mess inside and it is too cold to paint outside. I built a miniature spray paint booth out of a giant cardboard box. I cut a 19″x19″ hole in the back, taped a furnace filter over the inside of the hole, and put a box fan on the outside of the hole. The fan pulls air through the “booth” and out through the filter. Even though the “booth” is completely open on the top and front, the fan creates enough of a directional breeze to capture all of the overspray in the filter. The air moves so subtly, though, that it does not disturb the painting process at all.
I tested my mini-paint booth on the push-pull rods for the ailerons. (Click to see a larger version.)
I have a few steel parts that are not yet primed. For these, I will start with an SEM brand self-etching primer. I am mostly concerned with corrosion protection so, if the parts will not be visible, primer is all they will get. For parts that will be in sight, like the attachment of the axles to the main gear legs or the posts for the rudder pedals, I will add a layer of gloss black rattle can enamel paint, like you see in the photo above.
I decided not to corrosion-proof the whole plane, since most of the metal is “alclad” aluminum, which means that it was manufactured with a thin layer of pure aluminum over the alloy. This thin layer of pure aluminum quickly oxidizes and protects the aluminum alloy (the strong part of the metal) from corrosion.
Despite this, there are some aluminum parts that I want to paint (for appearance) or to which I want to add an extra layer of corrosion protection (because they might get wet). I decided to use Alodine for these. Alodine is a chromate conversion process, which actually changes the surface of the part from aluminum to a harder, corrosion-resistant metal. It also has a cool gold color and forms a very nice base for paint without adding any weight or thickness.
To Alodine a part, you soak it in Alumiprep first, an acid bath which cleans the surface and eats away any existing corrosion. Second, you rinse that off and then soak the part in the Alodine. Finally, you rinse the Alodine off and let the part air dry. Once dry, the surface is hard but, until then, you need to avoid handling it so that you don’t accidentally wipe off the Alumiprep coating.
Here is my first batch of parts, hung up to dry.
I tried using the Alumiprep and Alodine full strength and shortening the time that the parts were in the baths but am not happy with the results. The processes ran so fast that I was unable to control them to my satisfaction. You can see it in the finished parts, which are pretty dark instead of having a nice gold hue. For future parts, I will dilute the solutions 3:1 with water.
