Paul Eastham

Paul Eastham

Well Known Member
Hey guys,
Some of the alclad skins on my kit have gotten corroded where my sweaty arms or forehead (don't ask) have come into contact. I imagine blood and tears would give a similar effect.

It'll probably be 6 months before the airplane flies and 12 months before it gets painted. But the corrosion is noticable enough, and in prominent enough places, to bother me. It shows as a cloudy white area, not enough to feel with a fingertip though.

Is there something relatively easy I can do to inhibit or preferably remove this corrosion? I'm not interested in getting a motorized buffer or anything, but I'm willing to try to polish by hand...

Paul
 
sweat

paul i saw this on mine and have since been more careful. i sprayed some metal prep on mine and lightly rubbed with a green/grey scotchbrite. then you can poilish if you want buy hand. just go very lightly but enough to remove the corrosion. when you have removed it respary and give it a minute of dwell time before wiping off with water soaked rags a couple of times.i doubt its through the alclad but the longer it stays the sooner it will be.

if its minor enough you can forgo the scotch brite.
 
I used some aluminum cleaner I got from Wick's. Just wipe it on, let set for a minute or two and polish it off. It takes a little rubbibg, but takes all the corrosion right off.

Two problems with it though, the "black" stuff gets in around the rivets and is a little difficult to get out and second the aluminum you clean shines like a new baby's behind... care to polish the whole plane? :rolleyes:

Larry
 
I am using NUVITE polish...it restores the health of the alclad and removes the corrision. I had similar problems with plain old water spots after I washed off all the dust from fiberlass tip work. It takes a fair amount of elbow grease, unless you have a electric polisher...
www.nuvite.com
 
What types of aluminum cleaner or polish can safely be used if you intend to paint later? I don't want any primer or paint adhesion issues.

Thanks!
Scott
 
I am thinking that the polish is not an issue, because you still have to remove the corrosion, and etch the surface to prepare for priming??? The Nuvite simply removes the corrosion, then provides some surface protection.
I am NOT an expert on this....so I hope others that know more will chime in here...
 
Are you removing the corrosion because you don't like the look? Removing the corrosion doesn't stop new corrosion. Actually just removing the corrosion without protecting it will probably lead to more and deeper corrosion. If you really want to protect it you should alodine it and prime it. I am even a bigger corrosion freak in that I am putting proseal between every two pieces of metal. If you visit anywhere near salt water you have to protect the metal or will it corrode quickly.
 
Todd is correct in that polishing off the corrosion may only lead to further oxidation. In fact, any polishing of the alclad with an abrasive polish or scotchbrite will damage the alclad layer (which is basically a very thin layer of unalloyed aluminum) and expose the underlying material, which is more suseptible to corrosion.
When building my 9A, I subjected samples of both clad and unclad as well as alodined and zinc chromated material to ASTM accelerated salt spray testing. Without going into all of the results, I would only offer that I am surprised there is any visible corrosion on an alclad surface unless it was previously "polished". In any event, my suggestion would be to leave it alone, as final paint prep should involve a cleaning that will remove minor oxidation and at the same time etch or convert the surface to optimize paint adhesion.
 
When I was a gunnersmate in the Coast Guard we always had problems with certain people and corrosion during weapons training. Some people have acidic perspiration, which promotes a rust reaction within minutes. How many times I had to wipe the rust off of 45's after only an afternoon of use - and these were parkerized mind you...

If I were you, I'd keep as much of the blue protective plastic on the panels as long as possible, or primer the parts before assembly to avoid this problem in the future.
 
Keeping the blue plastic on doesn't always help. It will start to creep in on the sides. The only real corrosion you will probably see during the build process is to the alclad. Unless it takes you more than 5 years to build and and you leave the metal exposed to extreme moisture or salt air.
 
I'm hoping somebody can answer this with some certainty: Exactly how much sanding/polishing/scotchbrighting would it take to actually remove the cladding? My understanding is that it is .002-ish thick and soft, but wouldn't it take quite a bit of scrubbbing to remove that much?
 
Get a piece of scrap and polish a spot with scotchbrite. You'll be able to tell the difference in color when you get through the alclad.
 
sf3543 said:
Get a piece of scrap and polish a spot with scotchbrite. You'll be able to tell the difference in color when you get through the alclad.
Click to expand...

Just to make sure this isn't some type of snipe hunt, are we talking minutes, hours,...days? :)
 
Likely minutes. .002 of pure aluminum won't take long at all. It would be about like taking the paint off a soda can.
 
I just took a piece of .025 alclad, cleaned it, and mic'd it at .0255. I then got out the red scotchbrite and scrubbed steadily for a minute. I saw no change in color and it mic'd at .0254. I think I read that the alclad is around .001 and so I guess a minute of scrubbing gets me about a 1/10 of the way through the cladding.

I'm starting to think that there is a lot of misinformation (fear) about the fragility of the cladding. When you scuff, you immediately dull the shiny surface, but this does not mean the alclad is gone. I've read that Boeing polished a skin something like 300 times without removing the cladding. I'm also wondering whether there is actually a recognizable color difference once the alclad is gone. Any metal experts care to chime in.
 
I don't think just scotchbrite will do it. I remove the alclad with an orbital sander and 200 grit paper. It does take some effort.
 
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