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  #11  
Old 11-28-2022, 08:02 AM
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Mel Mel is online now
 
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I have to agree with Bob. I've seen a lot of older Cessnas with little to no corrosion.

I worked with "Corrosion Control" extensively on our C-124s in the Air Force, so I do know what corrosion looks like.
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Last edited by Mel : 11-28-2022 at 08:13 AM.
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  #12  
Old 11-28-2022, 01:52 PM
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Quote:
Originally Posted by David Paule View Post
Probably best NOT to bead blast the surfaces. Successful priming is achieved without that, with no damage to the alclad surface or the fairness of the part.

All you need is maroon Scotchbrite to abrade the surface and some suitable solvent to clean it. I've used lacquer thinner, denatured alcohol and isopropyl alcohol successfully for that, along with SEM, a couple of rattlecan zinc chromate or phosphate primers and Stewart EkoPoxy. Of those, the SEM and the EkoPoxy are the best.

The thread on Primers covers a multitude of opinions and comments and is worth reading.

Dave
+1. Bead blasting can also remove metal you would rather not remove. Trouble is, you won't be able to tell.....until......something breaks. In addition to heat warping, the heat can change the characteristics of the metal. Also, not good.
Maroon the parts, clean and prime away.

It's what I did and I have no regrets. The time, and cost is negligible compared to the near guarantee of no corrosion for difficult to see, mated parts. You will probably never sell your project, but if a prospective buyer is living in Biloxi, primer will be a selling point.

Just my $0.02.
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  #13  
Old 11-28-2022, 03:45 PM
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Quote:
Originally Posted by Mel View Post
I have to agree with Bob. I've seen a lot of older Cessnas with little to no corrosion.
I have too and more often than not they have varying degrees of corrosion. That said my Comanche has nearly zero corrosion and there is virtually no possibility of it internally as it was zinc chromated despite it having a rodent infestation at one point in its life. Rodent droppings release ammonia gas which creates a corrosive atmosphere.

Point is its better to have corrosion protection internally than not.
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  #14  
Old 11-28-2022, 05:37 PM
rocketman1988 rocketman1988 is offline
 
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Quote:
Originally Posted by rocketbob View Post
I have too and more often than not they have varying degrees of corrosion. That said my Comanche has nearly zero corrosion and there is virtually no possibility of it internally as it was zinc chromated despite it having a rodent infestation at one point in its life. Rodent droppings release ammonia gas which creates a corrosive atmosphere.

Point is its better to have corrosion protection internally than not.
It's certainly not going to hurt anything but it does take a bunch of time and adds weight.

It really comes down to, "Do you want an airplane that will last for 100 years or 150 years?"
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  #15  
Old 11-28-2022, 06:01 PM
MechaSteve MechaSteve is offline
 
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Quote:
Originally Posted by Wayne Stambaugh View Post
The surface left from the bead blasting supposedly relieves stress in the metal...
I actually did graduate research on this!

Bead blasting aluminum would likely have a similar effect to "Shot Peening" titanium. The effect is to actually CREATE residual stresses in the surface.

You can think of it as essentially compressing or burnishing the surface. Main difference is that the net shape and volume remains the same.

The positive result is that, ideally little to no material should be removed, and the resulting surface _should_ be more resistant to crack formation.
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  #16  
Old 11-29-2022, 03:30 PM
capshaw21 capshaw21 is offline
 
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Quote:
Originally Posted by rocketman1988 View Post
We will have to agree to disagree. Pretty sure I know the airplane after owning it for 20 years…
Red Scuff or sand with 220 grit and epoxy prime is best. Been painting for years and this is the best method.
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