Bike Friday bare exposed
 

https://cimg7.ibsrv.net/gimg/bikefor...c0404df55.jpeg
Bare metal exposed where seat post and bottom bracket make contact during riding. Anyone else experienced this. Do I have a henge problem.

Which BIke Friday is that? Is that the lower end of the seat tube? Mine aren't built the same way.

Model is NWT Silk. Drivetrain Rolloff 14 with Belt drive. The photo was taken with the bike upside down. The bare metal is on the bottom end of the seat post & bottom bracket

How old is this bike?

About 3 years 2022

looks like it was not cleaned/degreased properly before coating, reducing adhesion.

In that area inside the seat tube, and the exposed metal on the bottom of the bottom bracket, I would obtain a bottle of Ospho, it is a mild phosphoric acid solution (harmless if you get on your skin, but still wear gloves and glasses), apply with clean "acid brush" (cheap, disposable) or clean toothbrush or just paper towel, let sit for a day, that will (gray) phosphate the surface (a mild version of Parkerizing on military stuff), and that will give the paint better grip. These days, many car parts and body panels will be phosphated before paint. It also replaces primer. Apply second time if needed. Then clean area with alcohol, let dry, and paint. Bike Friday has used powder coating paint for a long time, so I don't think you can get touch-up paint, and for cars, that has gotten ridiculously expensive. I just look for the closest match in generic $3 nail polish, mixing colors if needed.

My folder has a fat aluminum seatpost, with an aluminum bushing (aka "shim") between the seatpost and seat tube, so at the bottom, there is clearance around the post; I think this is so that large welds in that area of the tubes, don't cause binding of the seatpost, due to any distortions in the tube. Bike Friday uses smaller seatposts from steel, and I think no bushing. I don't think there is any hinge problem.

yes, I tend to use jenolite rust converter clean it and in the seatpost, I would not bother painting; just a good amount of carbon paste (gritted grease).

For the outside, I'd get an automobive paint from autozon as it is likely to be better with bad weather.

To me that looks like the result of physical contact between the bottom bracket and the base of the seat tube.

Sir, this is a family website.....

Oh no...
https://cimg9.ibsrv.net/gimg/bikefor...ef50f60895.gif