Intergranular corrosion removal/retreatment

[Silvaire]

My A&P in Michigan identified what he said was IGC in my wing spar carrythrough. Caused (or triggered) by mouse pee. (Yes, the part had to be, and was, replaced.)

As I said earlier IGC is caused by an error in the manufacturing process, usually improper heat treatment. The term is often misused, it cannot be "triggered" by mouse pee. A good example is AD 96-24-17 on Luscombe wing spars. The AD calls for a one time inspection for intergranular corrosion. Either you have it or you don't. If you don't you're not going to get it later.

 

[Cap'n Jack]

Did every one who reads this understand that ?

I don't understand your point. We looked at the problem from different, equally valid, approaches and apparently came up with the same answer.

 

[Cap'n Jack]

As I said earlier IGC is caused by an error in the manufacturing process, usually improper heat treatment. The term is often misused, it cannot be "triggered" by mouse pee. A good example is AD 96-24-17 on Luscombe wing spars. The AD calls for a one time inspection for intergranular corrosion. Either you have it or you don't. If you don't you're not going to get it later.

Maybe not "triggered, but doesn't one need a liquid to complete the current which serves as an electrolyte in a battery? In electrochemical cells, a salt bridge serves the same purpose. The liquid completes the ionic circuit so the electrochemical reaction can continue. Remove the liquid, and the reaction stops, like removing the electrolyte from a battery. The electrons flow through the metal itself.

Although some of their terminology is questionable to a chemist, this FAA document describes my comment better, shows how paint can prevent corrosion, and shows the galvanic series that Tom was talking about.

https://www.faa.gov/regulations_pol...craft/amt_handbook/media/FAA-8083-30_Ch06.pdf

 

[Silvaire]

Yes but unless you're in a vacuum there is always moisture in the air so it's not really possible to completely eliminate it. I get your point though, mouse pee would certainly accelerate the process.

 

[Cap'n Jack]

Yes but unless you're in a vacuum there is always moisture in the air so it's not really possible to completely eliminate it. I get your point though, mouse pee would certainly accelerate the process.

That is why the FAA link I posted suggested paint which separates the liquid from the metal, to break the circuit. That is also one reason why unused planes are stored in desert locations. Water vapor doesn't carry ions as liquid water does.

Edit: the FAA link I thought I posted, it is in my comment now.