Polishing with two passes - Is that possible?

[berger]

Hi There,
My Waiex is in a bare finish since it has been built back in 2008.

Now, the aluminum is showing some tiny whitish flakes due to deeper oxidization which is taken place and I must go the polishing way.

I've carried out some accelerated corrosion tests within salty atmosphere on 6061 samples showing that a polished finish does withstand way better against corrosion than a bare or Scotch Brite finish. Stunning!

Also, I came across some "magical" products like California Custom Deoxidizer which I ordered and tested on scrap pieces. http://www.aircraftspruce.com/catalog/cspages/alumd.php
Basically, I think it is pretty clever to leave the chemical doing the work for you and it really does some cleaning in depth and the tiny flakes would vanish just by rubbing lightly the fluid over the surface with a rag. Though, I tested the product and it is very acidic with a pH of 2. So I guess it would not bee adequate to spread it over the fasteners.

Actually, using this Deoxidizer and Purple Metal Polish would produce a quite decent polish job in just two passes. No deep shine however, since this would not remove the grain of the surface. I've found that Belgom Alu polish would also produce a decent shine, even better than Purple, close to NuVite grade S.

I applied these chemicals by hand and do not know how this would work with a power tool yet.

Did someone else already tried this way with success ?
Any comments are welcome before I start on the real bird.

Thanks.
Have Safe Fun!

[MichaelFarley56]

I've used the Purple Polish as well as the green Deoxidizer in an effort to try and remove light surface oxidization from already polished skins. Personally, I really like the Purple Polish and think it's an excellent product; a little tough to wipe off but it cleans the metal skins very well. I've personally found the green Deoxidizer can be a challenge to use on polished skins because it beads off and once it's dry it leaves a film that's very tough to remove.

I'm planning on trying the combination of Deoxidizer and Purple polish on the unpolished skins on the bottom of my wings. If you try these products, please let me know how it works! I'm sure they will give you a shine but as you said, it won't remove the aluminum mill marks.

[berger]

I've used the Purple Polish as well as the green Deoxidizer in an effort to try and remove light surface oxidization from already polished skins. Personally, I really like the Purple Polish and think it's an excellent product; a little tough to wipe off but it cleans the metal skins very well. I've personally found the green Deoxidizer can be a challenge to use on polished skins because it beads off and once it's dry it leaves a film that's very tough to remove.

I'm planning to trying the combination of Deoxidizer and Purple polish on the unpolished skins on the bottom of my wings. If you try these products, please let me know how it works! I'm sure they will give you a shine but as you said, it won't remove the aluminum mill marks.

Hi Mike,

Thanks for your contribution.

In the mean time I started some real scale polishing on the fuselage of my Waiex. I noticed that the sheet section where I used the Deoxidizer just prior to applying NuVite F9 polish (in one pass only) would polish to a better shine than F9 with 4 passes. This was on the same sheet, so no difference in material grain or so.

So my conclusion is that Deoxidizer might remove some hard layer of aluminum oxide which then does save several passes of F9. But I also noticed that polish has to be used soon after the Deoxidizer has been applied and this is the way they suggest using it with the Purple Metal Polish as well. My guess is that the Deoxidizer is simply phosphoric acid which is known as an aluminum etching agent.

So I plan to polish my Waiex using essentially NuVite with a fresh application of Deoxidizer prior to initial polish, hoping to have a good polish job in just say 3 passes (F9, C, S).

However I wonder if this would be an issue to polish say F9 this spring and C say this autumn and S next spring?

Also I noticed that the under surfaces do not have the whitish tiny spots the sides and top surfaces have. I wonder if this has something to do with dust collected on these surfaces or only with condensed humidity from the unheated hangar (or both).

Guess that a cotton dust sheet after the polishing is complete would be a time saving idea.

Any comment on all these interrogations?

Thanks

[MichaelFarley56]

It makes sense that the deoxidizer is nothing more than a variant of an etching agent, designed to remove a thin layer of the aluminum. That would explain why I had so much trouble removing it after it dried on the skins.

I'm certainly no expert but if you're finding good results with the combination of deoxidizer followed by Nuvite F9 then I don't see an issue. I doubt one pass of F9 will remove much of the aluminum milling marks but if you're okay with that it won't be an issue.

I also doubt there will be an issue with spacing out the different polish grades over time, but if you wait too long and the skin starts to oxidize slightly (it does over time) you may need to repeat the C grade before working through to the S grade. I don't believe the S grade has much "cutting" power to clear up surface "haze" (oxidization).

Please keep us up to date on your progress and thoughts of the process. Thank you!

[berger]

Please keep us up to date on your progress and thoughts of the process. Thank you!

Hi,
Some updates on my recent observations.

Actually, the aluminum which was protected by the canopy tarpaulin has not a single sign of corrosion whereas the other exposed surfaces have these tiny whitish spots of corrosion. This would advocate for a cotton protection after polishing is complete.

The second observation is that the green acid helps in some cases, but if a in depth shine is desired, there seems to be no alternative to using NuVite F9 several times as many have said before. I noticed that applying some higher pressure would help reorganizing the surface with less passes. Of course this should be kept well within the ability of the sheet to withstand that pressure.

Will keep you posted as it goes...

[GraemeSmith]

My guess is that the Deoxidizer is simply phosphoric acid which is known as an aluminum etching agent.

From the MSDS sheet. The Green Deoxidizer is:

7664-39-3 hydrofluoric acid <1%

(Bit late to the party on this thread but as it came up when I was researching the stuff - I thought I would clarify for those that might follow).

For the stainless rivets:

Uses for hydrofluoric acid with stainless steel
Hydrofluoric acid is used in stainless steel pickling solution and paste preparations. Its main function is to loosen and help remove scale deposits. Incorrect use can be the cause of pitting problems if the solutions or pastes are left in contact with the stainless steel too long. It is very important that the manufacturers / suppliers instructions are followed to avoid damage to stainless steel products when using products containing hydrofluoric acid.

For the AlClad:

Hydrogen Fluoride (HF) will react with the surface of the aluminum and convert the aluminum oxide to aluminum fluoride. Water (H2O) is produced as a byproduct. In this way the HF works as a polishing agent to make the aluminum "shiny" again. Depending on the concentration of the HF, the contact time, and temperature, the HF can continue to react with the aluminum and corrode it.

[berger]

Thank you Graeme for your interesting post.
So it seems better to back off from the green deoxidizer (Purple Metal Polish system) for our Sonexes, due to the rivets corrosion hazards.