Empennage, Vertical Stabilizer (Part 7)

This afternoon I finished machine countersinking and dimpling the last few holes on the Rear Spar and Rear Spar Doubler.  The #30 holes in Rear Spar Doubler needed countersinking for AN426AD4 rivets.  Then, the corresponding holes on the Spar were dimpled with the DRDT-2.  Up until now, all the dimpling on the Vertical Stabilizer was for AN3 rivets, which uses a 3/32 Dimple Dies.  Because the Rear Spar and Rear Spar Doubler will be using bigger AN4 rivets, 1/8 sized Dimple Dies were used to dimple the Rear Spar.  Now, all the drilling, deburring, countersinking, and dimpling is complete on all the components that make up the Vertical Stabilizer.  

Now moving on to corrosion resistance!! There have been numerous debates and discussions among RV builders about corrosion resistance....how much, how little, what products to use, processes to use, best practices, etc.  Taking into account all the information and advice I've found online, and talking to many different RV builders, I have decided on the following corrosion resistance process and products on my airplane:

1.  Alumiprep:  Bonderite C-IC 33 Aero Acid Deoxidizer by Henkel.  It is also known as Turco Alumiprep 33 and is a phosphoric acid based cleaner, brightener, and pre-paint conditioner for aluminum.

2.  Alodine:  Bonderite M-CR 1201 Aero Chromate Coating (Alodine 1201) by Henkel.  Alodine is a chromic acid based coating chemical that produces a chrome conversion coating on aluminum and it's alloys.  The chrome conversion coating is very good for corrosion resistance and paint adhesion.  The chrome conversion coating forms a gold color on the aluminum being treated. 

3.  Epoxy Primer:  Akzo Fast Drying Interior Epoxy Primer by Akzo Nobel.  This is a chemically cured 2-component epoxy primer that provides maximum protection from various chemicals, hydraulic fluids, aviation fuels, and corrosive media.  Here is the Tech Data Sheet for the primer.  

The four pieces in the picture below were prepared as described in this EAA Hints for Homebuilders video.  The pieces were cleaned by being dipped in Alumiprep 33 (diluted 50% Alumiprep, 50% water) for two minutes, rinsed with fresh water, dipped in Alodine 1201 (no dilution)  two minutes for the chrome conversion coating, rinsed with water again, and finally hung up to dry.

 

The four larger pieces in the picture below were prepared by the same process.  However, due to their larger size, the Alumiprep 33 and Alodine 1201 were sprayed on each piece with a squirt bottle.  The Alumiprep 33 was sprayed on the aluminum piece and then scuffed with a grey Scotch Brite pad.  The Alodine 1201 was sprayed on the aluminum piece and then brushed on with a foam brush.  Each piece was rinsed with water between the application of each product and then again at the end.

Countersinking and dimpling the final holes in the Rear Spar and Rear Spar Doubler.  Also, you see the corrosion resistance process for the four smaller Vertical Stabilizer pieces.