Corroded Fuel Caps

[Tralika]

I'm building a kit that was produced in 1999 and has been in storage since. I opened my fuel caps for the first time and found corrosion on the nut that secures the cap locking mechanism. As you can see from the photo the corrosion is very advanced. The tanks were stored in a dry, heated garage. While the humidity here can run fairly high in summer, in winter it's not unusual for the humidity to be in the low teens. Certainly it's much drier here than in most parts of the country. I've found no other corroded parts so I suspect the tanks were leak tested with water and not completed drained/dried before being delivered to Just. If you are storing your fuel tanks for a long period I suggest you check your fuel caps from time to time. I'm going to start soaking the nuts in Liquid Wrench and try to get them off. With any luck the caps will be salvageable.

[danerazz]

Good argument for SS lock nuts on the caps.

[hoskinsb]

John,

My fuel caps looked exactly the same and I received the kit in August 2013. The nuts will come off OK and you need to take the entire cap apart anyway to do the fuel vent drilling. Wire wheel the nut or replace it and everything will be fine.

Happy Building

Brent Hoskins
Caldwell, ID
Highlander-flying

[SheepdogRD]

I'm building a kit that was produced in 1999 ...

You might want to check with the factory to see if your tanks were produced with resin that's incompatible with some of the chemicals in contemporary fuels. They made need replacing. It would be a shame to get the plane done, only to find you have leaky tanks that force you to tear the wings apart ...

[jak]

This is a common problem I see it all the time they come to us that way sometimes I've never used anything but a 9/16 wrench to get the nuts off (replace them) and clean the rest. Jak

[Tralika]

The corroded nuts came off easily and the other parts cleaned up nicely with some solvent. I replaced the rusted nuts with aviation steel elastic lock nuts but now I'm wondering if a stainless steel might be better. This corrosion was really advanced and that makes me wonder if there is a reaction between the steel nut and alloy fuel cap body. Another option might be a nylon washer between the nut and fuel cap body. Any metals experts have an opinion? Also, anyone seen any corrosion when the caps are in use exposed to gasoline rather than in storage?

[danerazz]

I still vote SS in this case, I am less worried about structural strength here than contamination.