Spar corrosion? Need advice

[samiam]

Hey all,

I purchased a 2nd hand kit that was sitting in a garage for 10 years. It had the prebuilt spars, which I have been working on attaching the angles to. On one side of one of the spars, I found this:

https://drive.google.com/open?id=0B0U7g ... tiTnhuRFhn

I have no experience with corrosion but think that is what this is. It easily comes off with a fingernail, but leaves a little bit of white discoloration behind.

Can other builders provide any advice? I am hoping scotch brite down to clean metal then prime?

I really need to get a tech counselor in here, but I'm leaving for vacation tomorrow and just want some reassurance that I can salvage this and wont have to sink thousands into new spars.

[mike.smith]

I'm no expert, but it looks and sounds like very minor stuff. I'm not even sure it's corrosion, as much as it may be minerals that have crystallized from moist air. 6061T6 is very resistant to corrosion. If it cleans up and doesn't leave deep pits then you're likely fine. It never hurts to run things by the Sonex factory, though of course you won't be able to contact them until next week.

[tonyr]

Hi Mike

Its minor surface corrosion, most likely caused by accumulated dust and moisture. I have had a fair bit of it over the years on 6061 stock. Even on my completed aircraft, this winter under the fuse and wings I have the same. Doesn't help being parked over carpet thats covering a dirt floor.
If you get a scotchbrite maroon pad and have a go at it, it will come off easy. I cut up some pads to make a bunch of discs bolted together. Mounted in my cordless drill it made the job easier.
You might find a bit of whats known as filiform corrosion underneath it, which will be dark and squiggly like on the bare metal. You can go harder with the scotchbrite to get this off as well. You wont damage the metal.

The key with stopping this type of problem is keeping it dust and moisture free.

Cheers
Tony

[Darick]

Hi Mike,
Corrosion X or similar products will prevent that from happening next time.

[samiam]

Thanks for the input everyone. That really helps. It does come off very easily. It leaves a discolored spot behind, which takes a lot of rubbing with the maroon pad to get off - not sure if it is essential to do that or not.

I'll be back at it next week.