sporran

sporran

Member
My Vertical stab has been lying in an unheated attic with blue plastic removed for just over two years, I dusted it down yesterday and found some surface corrosion which I assume is filiform corrosion (the side the was lying against the particle board that floors the attic).

I've cleaned the surface with MEK, and here's what I've got:

241106_VS_surface_corrosion.jpg


and

241106_VS_surface_closeup.jpg


There appears to be no pitting, it's pretty smooth to the touch and looks better in real life compared to the photos. I assume moisture has become trapped between the VS and the flooring since it only appears on the part that was effectively resting against the floor (all other empennage parts are ok).

Searching previous posts on similar types of corrosion have been fairly helpful (and reduced my blood pressure), however the common tread is if you've got some corrosion ask an aircraft engineer or mechanic as they see this type of stuff daily.

So my question is do I deal with the corrosion now, or wait until I'm ready to paint the completed aircraft (about 2 years away from that).

Richard
 
Hey
Deal with now!!!!!!!!!!!

srub it with a scochtbrite pad or similar and then prime it with a good primer

had similar problem on some edges and where the blue text on alu was

sincerly
Jorn Moller
OY-RVS RV8
300 hours
 
Since the skin is still bare, it's not filiform corrosion - that only forms under paint of specific types. Looks more like a minor case of surface corrosion.

I'd recommend scrubbing with maroon Scotchbrite. Use one piece to knock the worst of the corrosion off, then use fresh pieces to finish, so you don't end up burnishing the oxides into the skin. Alodine the area you scrubbed (since the Alclad is gone), then prep and prime the whole assembly with the potion of your choice.
 
For the past several years, Chaile Kuss and I give a workshop at Sun n Fun on Aluminum corrosion prevention.

I would use a fine (blue) scotch-brite surfacing disk or equivalent, etch the skin with Alumiprep ( phosporic acid ) and then Chromic convert the surface using Alodine or Iridite 14-2 made by MacDermid. Prime the the skin with a mil-spec two part epoxy primer.

Then you can store your parts for the next fifty years and it won't corrode!

If you would like the details on the particulars on how to to do this, give me a call.


Peter Laurence
786 210 4867
 
Priming the outside it is.

Thanks folks, particular of interest was Steve's link to his comments on removing the blue letters on the alclad - wish I'd known that three years ago.

I'm going to remove the corrosion and prime the VS as soon as I can get my hands on some Randolph White Epoxy primer - the green stuff isn't what I want under the top surfaces.

Obviously the safer, long term, storage soloution would be suspend the parts with enough of a gap around to let the air circulate - you live and learn.

Richard
 
The weird thing is that the blue ink comes off with WATER and not some petroleum products!

Anyone else notice this?

:D CJ
 
Water soluable

CJ - yes, thats right. The problem is because it is water soluable and (I think therefore ) hygroscopic.

I suggested VANS ask Kaiser to print on the plastic (others do) but they were not too interested. The corrosion problem is ours, not theirs.
 
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