Well for one thing, the flush valve or how it seats to the wing has failed.

The only steel in the tank is the fuel cap (up to 1978) and the fuel float sender in the tank wingroot. If this rust cause the place sat near empty for a while it will rust since the tanks are vented. Keeping them filled now stops new rust.

We just had this problem on a Tiger and with the rusty fuel sender, we pulled the left sump tank and flushed it three times to get it to run clear. WE installed an overhauled unit with a new gasket.

Video on our Channel ‘Grumman Pilots”

https://www.youtube.com/edit?o=U&video_id=UVnBH5qRaus

So that is the rust story.

Cheers

Roscoe