Pros and Cons of Polished Aluminum

How to keep the Cessna 170 flying and airworthy.

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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.
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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.
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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.
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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
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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
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Re: Pros and Cons of Polished Aluminum

Postby IP076 » Wed Aug 21, 2019 10:46 pm

Hattrick wrote:That's the one I'm looking at in person tomorrow. Hopefully she's as pretty in person up close. If so, I'll be putting a deposit down. Now I need to find an A&P that can help me with a prebuy...


Did you get it?

I made a call, obviously too late. I wish folks would take down an ad that has already sold.
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Re: Pros and Cons of Polished Aluminum

Postby Hattrick » Wed Aug 21, 2019 10:59 pm

IP076 wrote:
Hattrick wrote:That's the one I'm looking at in person tomorrow. Hopefully she's as pretty in person up close. If so, I'll be putting a deposit down. Now I need to find an A&P that can help me with a prebuy...


Did you get it?

I made a call, obviously too late. I wish folks would take down an ad that has already sold.


No, I looked at it in person but between the seller's unfortunate attitude and the handful of problems I saw before paying for the prebuy I walked away. Good thing for me because I'm currently looking at a much nicer 170! I also think I've decided that while polished aluminum looks sexy, I don't think it's for me.
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Re: Pros and Cons of Polished Aluminum

Postby IP076 » Wed Aug 21, 2019 11:38 pm

Hattrick wrote:
IP076 wrote:
Hattrick wrote:That's the one I'm looking at in person tomorrow. Hopefully she's as pretty in person up close. If so, I'll be putting a deposit down. Now I need to find an A&P that can help me with a prebuy...


Did you get it?

I made a call, obviously too late. I wish folks would take down an ad that has already sold.


No, I looked at it in person but between the seller's unfortunate attitude and the handful of problems I saw before paying for the prebuy I walked away. Good thing for me because I'm currently looking at a much nicer 170! I also think I've decided that while polished aluminum looks sexy, I don't think it's for me.


For the brief moment I talked to him on the phone he didn't sound like the happiest of folks. Hope the next one works out! I'm also on the fence about the polished finish, looks great, but at what effort? I'm just getting started in my search myself.
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Re: Pros and Cons of Polished Aluminum

Postby c170b53 » Thu Aug 22, 2019 3:29 am

Hat trick, can you shoot the puck on what you saw as problems ?
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Re: Pros and Cons of Polished Aluminum

Postby Hattrick » Thu Aug 22, 2019 3:43 am

Sure! First thing I noticed was gray painted flaps and ailerons (instead of polished aluminum like rest of aircraft) which was not disclosed before driving 9 hours round trip to see the plane. Then I noticed that landing and strobe lights were not working. Extensive hail damage to horizontal stab and elevator. Minor damage/bending to bottom of rudder and tips of each elevator. The advertised engine compressions were from an annual completed 5 years ago, which was the last time the plane was annualed. Tach showed 17 hours in the years since the last annual. Headliner needed to be replaced at some point. Owner refused to fly the airplane (once the annual was documented in the logbooks). Decided it wasn't worth my time or money. I'm sure a proper pre-buy would have uncovered several more issues since this is just what I could see with my own eyes. I won't get into the owner's attitude but there was definitely no negotiating of the price. As is sale. So I decided that this particular 170 was not for me.
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Re: Pros and Cons of Polished Aluminum

Postby cessna170bdriver » Fri Aug 23, 2019 3:09 am

c170b53 wrote:Hat trick, can you shoot the puck on what you saw as problems ?

This question was the clue that told be how Hattrick is supposed to be pronounced. I doubt that very many folks who grew up south of about Ohio will get it. (I wouldn’t have gotten it before I married a girl from Michigan.) :lol:
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Re: Pros and Cons of Polished Aluminum

Postby 4583C » Fri Aug 23, 2019 8:47 am

cessna170bdriver wrote:
c170b53 wrote:Hat trick, can you shoot the puck on what you saw as problems ?

This question was the clue that told be how Hattrick is supposed to be pronounced. I doubt that very many folks who grew up south of about Ohio will get it. (I wouldn’t have gotten it before I married a girl from Michigan.) :lol:



Even I had that one figured out Miles!! Now don’t ask me what “Hat Trick “ is beyond a hockey term.
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Re: Pros and Cons of Polished Aluminum

Postby Hattrick » Fri Aug 23, 2019 1:12 pm

4583C wrote:
cessna170bdriver wrote:
c170b53 wrote:Hat trick, can you shoot the puck on what you saw as problems ?

This question was the clue that told be how Hattrick is supposed to be pronounced. I doubt that very many folks who grew up south of about Ohio will get it. (I wouldn’t have gotten it before I married a girl from Michigan.) :lol:



Even I had that one figured out Miles!! Now don’t ask me what “Hat Trick “ is beyond a hockey term.


HA! What can I say... I'm a huge hockey nut!!! I figured most guys would make the connection. At least I didn't go with something like "5Hole" or "SinBin" :lol:
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