Pros and Cons of Polished Aluminum

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Re: Pros and Cons of Polished Aluminum

Postby lowNslow » Tue Aug 13, 2019 2:32 pm

dstates wrote:
lowNslow wrote:The problem with polishing is you are slowing removing the surface alclad layer of pure aluminum from your aluminum surfaces which is there to prevent corrosion of the aluminum alloy core material. As nice as it looks I think painting or using George's technique is the way to go.


I went to the Nuvite forum this year at Oshkosh and the presenter talked about this, she said it would take over something like 150 heavy cut polishing passes to get through the alclad layer...

She may be right but she is also trying to sell polishing product.
Karl
'53 170B N3158B SN:25400
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Re: Pros and Cons of Polished Aluminum

Postby gahorn » Wed Aug 14, 2019 10:05 am

From a simple Google search:

ALCLAD 2024 "Nominal cladding thickness is 5% on gauges under 0.062 in. (1.57 mm) or less; 2.5% on gauges over 0.062 in. (1.57 mm)." This amounts to only 0.0016 inch for 0.063 inch material.

For an electropolishing process with longer cycle time and amp-minutes, as much as 0.003″-0.005″ of material may be removed depending on process conditions.

While I don’t believe most people polish-away all the cladding... I just wish to point out how subjective this topic actually is.... it depends on what is meant by “heavy” and “polishing”. It should be obvious that material is actually being removed by polishing.... just as it should also be apparent that polishing will remove surface material (including a form of early-oxidation/corrosion called tarnish)..... after-all, that IS the intent!
Just don’t fall for the claims that it doesn’t materially affect ALCLAD... (or that properly polished aluminum will quickly corrode)... If it’s kept CLEAN and DRY it will remain good-looking a long time (and without incessant polishing.).
I believe it’s true that N146YS was polished only once in it’s life (when it was restored) and hasn’t been polished for over 22 years now and you can see pics of it from this years convention.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight.
An originality nut (mostly) for the right reasons. ;)
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Re: Pros and Cons of Polished Aluminum

Postby n2582d » Wed Aug 14, 2019 1:35 pm

George,
It’s no wonder you haven’t polished your plane in 22 years! Electropolishing an entire airframe would be a royal pain to say the least — not to mention the difficulty of finding a dip tank large enough to immerse the fuselage and wings.:wink:
Gary
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Re: Pros and Cons of Polished Aluminum

Postby gahorn » Thu Aug 15, 2019 2:52 am

Perhaps the term was not comletely understood, but I took it to mean mechanical polishing with electric-orbital polishers such as those often sold for the purpose...not submersion de-plating. Like I mentioned... it was a simple google search.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight.
An originality nut (mostly) for the right reasons. ;)
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Re: Pros and Cons of Polished Aluminum

Postby hilltop170 » Thu Aug 15, 2019 8:37 pm

My understanding of metallurgy says George is correct and Cessna got it right to start with to not polish its new planes.

Alclad has a pure un-alloyed aluminum outer layer that is there for corrosion protection of the base alloy below it. The Alclad outer layer indeed corrodes as George’s plane demonstrates but at a much slower rate than the alloyed aluminum beneath it. This aluminum oxide corrosion “passivates” itself which inhibits further corrosion.

Polishing removes the oxide layer and without protection, it will oxidize again. So the question is, do you leave it alone and let it passivate, polish it again and again, or protect it with paint? The owner has to decide what look they want the plane to have and how much effort and money they are willing to spend to get it.
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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Re: Pros and Cons of Polished Aluminum

Postby ghostflyer » Fri Aug 16, 2019 12:01 am

It’s great to have a polished aircraft but some of the environments that they live in [ coastal] have a detrimental effect on raw Alcad.
Painting is the only answer and washing in WD40 and water slows down the corrosion. There has to be only a very small mark on alclad [finger print] and the corrosion process has started. However with nano ceramic technology, good results have been shown . Eg Johns 360 product . I am not endorsing the product but sitting on the fence to see how it develops .
But have heard very good reports .
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Re: Pros and Cons of Polished Aluminum

Postby hilltop170 » Fri Aug 16, 2019 12:51 am

I see a totally bare unpainted 1965 Chevy every year for the last 3 years at Palmer, Alaska car shows. The guy uses a corrosion preventative product called Gibbs. He wipes on a coat every year and that is all he does.
Gibbs claims it works on aluminum. https://www.gibbsbrandlubricant.com/

9CAAF6F6-9575-473A-B483-62C6B4C516CA.jpeg
Bare metal 1965 Chevy
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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