Letter 40034

Pitting in 2024-T4 used in aerospace  

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Hi,

Just a question, has anyone ever experienced pitting corrosion in the 2024-T4 material. EDS shows that chlorides are present in the pits. Is it the process line, or something else.

Your help would so greatly appreciated.

Jason Sighn
aerospace - Vancouver, BC, CA

Chlorides from dragged in tap water and/or fluorides from proprietary products anywhere in an aluminum treatment process line will cause pits. This is agravated by the galvanic action between titanium racks and stainless steel tanks or heaters.

In old 2024 or heat treated 2024, the copper has migrated to the grain boundaries, where it is more rapidly picked out by chlorides and/or galvanic action, thus leaving behind pits.

Do a labaratory line with beakers, D.I.water, and fresh make-ups, and see if you can confirm what I have said above.

Robert H Probert Robert H Probert Technical Services Garner, North Carolina Editor's note:        Mr. Probert is the    author of Aluminum How-To / Aluminio El Como