Hey CD,
So I’m sure this is something that a lot of teams encounter, and its definitely something that occurs in industry quite frequently…
You machine yourself a beautiful looking part. You clean it up, sand it, scotch-brite it and after a few hours or days the part looks dull again (it oxidized). I’m referring specifically to aluminum parts, but it has occurred with other materials too. I was wondering if anyone had a tip on sealing parts that have been polished or cleaned. There are sealants you can buy, but my inclination was telling me theres gotta be some tips out there. So, anyone got anything?
No real way to prevent this on aluminum parts without some sort of coating. This is why most aluminum parts in commercial products are anodized. The simplest, cheapest, fastest drying clear coat is just the clear spray paint you will find in most spray paint collections at the hardware store. Krylon and most other brands have a clear paint. Comes in gloss,satin, or flat like other paints. Polyurethane or other clear wood finish can be used, but can leave a slight yellow tint. Clear laquer can give a very nice shiny finish, but takes a long time to dry. The best choice for a hectic build season is probably clear spray paint.
On the robot parts we want to be shiny, we usually wet sand up to about 2000 grit, then polish with a compound on a cotton buffing wheel, and they come out looking like this. This part has not really dulled at all over the season, but our robot has not been subjected to any sort of wet or humid environment.
To keep it shiny, you could wax it with some sort of car wax or synthetic sealant, but that would wear off over time. The only sure way to keep it shiny is to polish it again, or cover it with a clear lacquer or urethane as mentioned above.
Move to Arizona. Seriously…bare polished aluminum stays shiny for years here, especially if kept indoors. I have bare sandblasted steel parts in my garage that have been sitting there for years with no rust forming on them.
Just remember that if you paint or wax your aluminum parts that you will have to remove the coating should you wish to weld to them. We’ve thought about painting our frame from time to time, but have decided to not do it in the event we need to make last minute additions or modifications… or worse… repairs.
For the shiny parts we’ve just buffed them on the buffing wheel which leaves a nice shiny finish with a bit of wax on it, and the parts have stayed shiny for a long time… even here in the Pacific Northwet.
One thing I wanna comment on is you may not necessarily remove the oxidized aluminum. Alumina (Al2O3), as it’s referred to, is actually one of the hardest natural materials, second only to Diamond. Removing this Alumina actually weakens the piece, and could potentially result in structural weakening.
My team always used to make our aluminum look shmexy with different ways. We simply used a wire brush and brushed patterns into the metal, tedious, but well worth it in my mind. http://www.team811.com/photo/main.php?g2_view=core.ShowItem&g2_itemId=6739
The benefit of this was the aluminum could still oxidize and have its strength, as well as looking real good!
All other things being equal, a better-looking airplane always does better than a not-so-good-looking one. [R/C piloting wisdom]
Some parts you do want a bit duller, like anything with a coating of grease. But the main reason to have the robot shiny is so that the robot looks more professional and catches more eyes. This is especially important come Saturday near lunchtime, as teams try to remember who is good enough to pick. A professional-looking robot will help jog their memories, provided that it doesn’t do really poorly on the field.
