Treat minor filiform corrosion

GlennAB1 said:
AC 43.13 requires corrosion blend out and polishing afterwards. You haven't done that. Your finished lap seam has pits, tool marks, scribe lines, scratches, elongated holes from misdrilling. Metalsmith?
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More bloviation , I'm certain you can tell from the pictures..

but you should do more internet research, try watching this,

 
GlennAB1 said:
Bull. AC 43.13-1A, dated 1988 was cancelled when AC 43.13 1B came out in 1998.

Maybe you can, but it's obvious you've sanded. The scratches left behind extend from the metal onto the orange paint.
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Not even a little bit.
 
GlennAB1 said:
AC 43.13 requires corrosion blend out and polishing afterwards. You haven't done that. Your finished lap seam has pits, tool marks, scribe lines, scratches, elongated holes from misdrilling. Metalsmith?
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You go right ahead and blend a .016" skin. That statement is about the stupidest statement you've made.

And proof you are just making stuff up as you go. Because had you ever opened a factory seam you'd know what you were looking at
 
I'm thinking it is bunny time. Bunny with a sandwich? That would make things better! :)
 
Can I get an AMEN???
 
Tom-D said:
And proof you are just making stuff up as you go. Because had you ever opened a factory seam you'd know what you were looking at
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Bull. You have no clue about the responsibility of an inspector at an airline. Do you even know what Required Inspection Item means? I've been involved with hundreds, if not thousands, of factory seam (lapseam and circumferential) inspections and repairs. We buy off every step of the repair process, including determining if blend out is sufficient or whether reinforcing or replacement is required. The pictures you've provided are clear enough for me to know that it is actually worse than it appears, which means you're doing a **** repair on a **** aircraft that you've made clear is for the sole intention of profiting.
 
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Tom-D said:
fact is, no one taught you general shop practices,
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Tom-D said:
Folks, Glen must have forgotten that they teach General shop practices in
A&P school. and their curriculum is approved by the Administrator. :)
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Alright, since you keep bring up "General shop practices" and curriculum requirement, let's discuss it.
I surveyed quite a few A&P co-workers, and the ones that went to a part 147 school pretty much had the same experience I had.
No one did any corrosion removal of any type.
We all did a couple small projects that included sheet metal layout, forming, bending, and riveting. Then we damaged our projects and 1. blended and alodined an area, and 2. stop drilled or cutout damage and made a reinforcing repair.
That satisfies the curriculum requirement in Part 147, Appendix C, you wrote about.
To attempt to BS everyone to believe that A&P schools have the resources, or are required to teach corrosion removal to 20 or so individuals every simester, is pure nonsense.
 
Hey Tom, while we're on the subject, what Part 147 A&P school did you attend that allows you to cite a training curriculum, anyway?
 
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GlennAB1 said:
It's already been determined that AC 43.13 allows for the use of a specific stainless steel brush , with specific followup steps. Tom uses and does neither.
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Due to the ****ing contest there was no way to tell. Sadly the OP is still looking for help to his original question. There has been a bunch of quoting mindless drivel that really does not add to answer to the question. Hey do you work for the FAA by chance?
 
Then what is the point of all the AC/regs you post if they don't help solve the question? How would you fix the OP issue?
 
Did OP not state that they would have another A&P look at it?

How would I fix OP's issue?

I'd remove paint from the suspect area. If it's corroded, I'd remove the corrosion with Scotchbrite and/or an aluminum oxide type abrasive. I'd make a determination if the damage cleanup was acceptable as is, or whether a strengthening repair is required. If not, I'd treat, prime and paint.

And I'd base my determination on:
1. Manufacturer's manuals.
2. AC 43.13-1B
3. Standard Industry Practices that have been found acceptable that I can produce.

Not some made up BS about A&P school general shop practices, when (as I understand it) he never even attended A&P school.
 
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Rustoleom makes good stuff, and that might actually be great stuff, but I probably wouldn't. Without doing indepth research I would use someting I know, and has industry approval. That would be a zinc chromate primer, or Boeing approved green primer. If interested I can probably find vendor source info when I get back to work next Monday.
 
clean, prep, apply paint.....if it doesn't work it will blister again.....rinse and repeat with your second choice. It won't be turning to salt that fast.
 
When Glen advises Abrasives should be used to remove the corrosion products, he doesn't know the only real long lasting corrosion protection (the Al-Clad layer) will be removed too.

If you do not want to make matters worse, do as I advised long ago in this thread.
 
yetti said:
Due to the ****ing contest there was no way to tell. Sadly the OP is still looking for help to his original question. There has been a bunch of quoting mindless drivel that really does not add to answer to the question. Hey do you work for the FAA by chance?
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He has already been advised how to treat this problem in other message form. where the bum dope is eliminated.
 
GlennAB1 said:
It's already been determined that AC 43.13 allows for the use of a specific stainless steel brush , with specific followup steps. Tom uses and does neither.
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How do you know what Tom does? just continuing the Pizzing contest again? You've proven time and again you have no idea how to work on small aircraft.
 
GlennAB1 said:
Hey Tom, while we're on the subject, what Part 147 A&P school did you attend that allows you to cite a training curriculum, anyway?
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If it were any of your business you'd know already.
 
GlennAB1 said:
It's already been determined that AC 43.13 allows for the use of a specific stainless steel brush , with specific followup steps. Tom uses and does neither.
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Why do you refuse to believe the 43,13 has no application on aircraft that have their own manuals. you should actually read the purpose of the AC.
CC268 said:
Can I get an AMEN???
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amen.
 
Tom-D said:
When Glen advises Abrasives should be used to remove the corrosion products, he doesn't know the only real long lasting corrosion protection (the Al-Clad layer) will be removed too.

If you do not want to make matters worse, do as I advised long ago in this thread.
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Well, since it's corroding already, that tells me the AlClad layer is gone already, might as well get down to clean metal and treat it properly to prevent a reoccurrence.
 
teejayevans said:
Well, since it's corroding already, that tells me the AlClad layer is gone already, might as well get down to clean metal and treat it properly to prevent a reoccurrence.
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In a very small area, want to make it bigger? want to see it corroded a larger area again?

Remove the blistered paint chemically, remove the corrosion products chemically, agitate with a plater's brush until clean. alodine, and paint. that will repair the damage as well as it can be.
When you scratch or dig with hard tools, you simply make matters worse. when it re-occurs after you have removed material, you'll simply make a hole in the sheet skin trying to do the corrosion removal the second time.
Belly skins on a Piper are not made in the field, they are a stamped part, piper is the only one making them. So if you'd like to spend 15-20k having the skin replaced, you'd be placing a patch on the corroded area. Might have better done the corrosion repair correctly the first time.
 
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and since Tom knows more than Glenn....do what Tom sez. If that don't work try Glenn's ideas.
 
teejayevans said:
Well, since it's corroding already, that tells me the AlClad layer is gone already, might as well get down to clean metal and treat it properly to prevent a reoccurrence.
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OBTW, the corrosion may not go all the way thru the al-Clad, want to make sure it does? sand away anything that is left, Yeah, lets do it Glen's way and make sure it does expose the base metal.
 
Checkout_my_Six said:
now don't get all big headed over that....cause you don't know how to operate a nuclear resonance sonar scanning micrometer machine.:lol:
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I'm just an old mech that has been fighting corrosion most all my adult life. So I wish I knew what the hell you are talking about. :)
 
yetti said:
I vote with Tom on the stainless brush. That is what is recommended for prep work prior to welding aluminum.
https://www.millerwelds.com/resourc...luminum-filler-and-base-metals-before-welding
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but when you use them to remove corrosion, you use them a bit different. you do not want to use a brush stroke. you operate them in a small circular motion as to not leave long scratch marks. all you want to do is agitate the corrosion products and allow the etch (aluminum-prep) to do the cleaning. the whole thought is, "don't remove any aluminum"
 
Tom-D said:
In a very small area, want to make it bigger? want to see it corroded a larger area again?

Remove the blistered paint chemically, remove the corrosion products chemically, agitate with a plater's brush until clean. alodine, and paint. that will repair the damage as well as it can be.
When you scratch or dig with hard tools, you simply make matters worse. when it re-occurs after you have removed material, you'll simply make a hole in the sheet skin trying to do the corrosion removal the second time.
Belly skins on a Piper are not made in the field, they are a stamped part, piper is the only one making them. So if you'd like to spend 15-20k having the skin replaced, you'd be placing a patch on the corroded area. Might have better done the corrosion repair correctly the first time.
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You are required to blend the damage to remove stress risers.

Tom's lapseam is an excellent example of what he is preaching not to do. He's scratched the hell out of the entire lap with a harder material. He says it's not enough to damage to cladding. That's BS. There is no way he knows that. The cladding was probably only a little over 1/1000" thick when new. His lap seam is full of stress risers that once closed back up can hide a crack the forms beneath.

As aircraft owners you are responsible for the airworthiness of your aircraft. If you're ok with doing just enough to make a buck, do what Tom says. But if your airplane is a keeper and you don't want to continually revisit corrosion, do it right. I assume you all can read. Read your manufacturer's maintenance/structures manuals and/or 43.13. Please do that, and make the call as to how your aircraft is maintained.
 
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Tom-D said:
but when you use them to remove corrosion, you use them a bit different. you do not want to use a brush stroke. you operate them in a small circular motion as to not leave long scratch marks. all you want to do is agitate the corrosion products and allow the etch (aluminum-prep) to do the cleaning. the whole thought is, "don't remove any aluminum"
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A case of do as he says, not as he does. His lap seam definitely has long scratches.

And, you have to remove material if you want to remove stress risers.
 
Tom-D said:
OBTW, the corrosion may not go all the way thru the al-Clad, want to make sure it does? sand away anything that is left, Yeah, lets do it Glen's way and make sure it does expose the base metal.
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Given skin material this thick:
Tom-D said:
You go right ahead and blend a .016" skin.

<SNIP>
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Just how thick is the aluminum cladding?
 
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GlennAB1 said:
Cladding thickness varies, it's usually between 2 to 5 percent of the overall thickness. Thicker alloy having thicker cladding.
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So, that's about 20 micrometer thickness (0.016" to mm *.05) maximum.

Is it reasonable that the corrosion in the original post is because Al cladding has been breached? After all, my understanding is that the Al cladding has a protective layer of Al2O3. A minor breach of this layer should just oxidize again to reform the protective barrier, but a scratch deeper than 20 micron would expose the load-bearing skin underneath and allow it to corrode.
 
GlennAB1 said:
20 micron. high equates to about half the thickness of a human hair.
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Yes, I understood that, and that's my point. The cladding is thin, and made of a soft metal. That suggests the comment below is correct.

teejayevans said:
Well, since it's corroding already, that tells me the AlClad layer is gone already, might as well get down to clean metal and treat it properly to prevent a reoccurrence.
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Tom-D said:
In a very small area, want to make it bigger? want to see it corroded a larger area again?

Remove the blistered paint chemically, remove the corrosion products chemically, agitate with a plater's brush until clean. alodine, and paint. that will repair the damage as well as it can be.
When you scratch or dig with hard tools, you simply make matters worse. when it re-occurs after you have removed material, you'll simply make a hole in the sheet skin trying to do the corrosion removal the second time. Might have better done the corrosion repair correctly the first time.
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No, but you do not want the chemicals you are using to remove the paint and corrosion products to do it that either or react with the aluminum, remaining on the surface to cause for corrosion.
I'd at least check they are safe to use with aluminum, unless there is something you had in mind.
Aluminum is stamped, cut, drilled during manufacture so it can be done.
 
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