Bottom bracket rust on my '51 Sun Wasp
 

I've got the Wasp on the stand to put in a good cartridge BB and get the bike set up for rainy autumn fixed-gear commuting. Either I hadn't noticed when I put in the cup-and-cone BB a year ago, or it has gotten rather worse - but there is some flaking rust within the BB shell that is concerning, or at least it appears to me to be concerning. There may be a small spot where it goes all the way through. I haven't taken the brush to it yet to know for sure, but at first glance - what do you think? I realize that this frame is 71 years old, but being DB 531 its a really great rider and I want to keep it for the long haul. My plan was to someday send it "home" to Mercian in the UK for a full resto and enamel job. Anyway, that's not in the cards just yet.

https://live.staticflickr.com/65535/...42bbafce_k.jpgPXL_20220815_232449898

Thanks.
Ged

Get it all cleaned out and see how bad it is, if its all the way through then it may be time for a creative cutout, rust convertor, paint/seal, frame saver throughout and the sealed BB.

I own an un-galvanized boat trailer that is used in salt water so I am no stranger to rust. I don't think yours looks too serious. Rust has a much greater volume than the iron that created it so when you get that scale removed I think you will find you haven't lost that much of your bottom bracket after all. Even if it has perforated, remember that many high-end bike builders deliberately cut out material from that area so I wouldn't conclude that the BB is structurally compromised. Spraying some kind of anti-corrosion stuff (Frame Saver, Boeshield, etc.) inside the frame is probably a good idea. Sometimes the interior of old frames were treated with linseed oil when first built but that has probably long since dried up by now.

Thanks guys. I'm going to get it cleaned out and get some primer on there, and get frame saver in all the tubes.

One of my bikes had a BB with a touch of rust (not bad at all but I’m a hypochondriac regarding structural integrity) so I showed it to gugie and he gave me reassurance by informing me that the BB is the strongest part in the frame. Good enough for me and the bike is brilliant to ride.

From the description it is time for an oxalic acid solution bath or Exrust

at least the inside of the tubes and chainstays.

.
...that looks like the stuff that flakes off and drops down from the interior of seat tube, mostly. There's a way to fit a round wire brush of the appropriate size diameter to a wooden dowel, and use it to clean out most of the surface rust inside the seat tube. It;s the same wire brush they sell at hardware and home improvement stores, to use when brazing and soldering copper plumbing pipe. You need to remove the handle, and replace it with the longer wooden dowel. Then you just run it up and down the seat tube, and clean out all the rust junk that drops into the BB shell. The you can also use the round wire brush to kind of clean out the BB shell, of any rust on that surface as well.

The final step is to spray the interior of all the tubes with something like this stuff (also available at hardware stores, or online.) You squirt it in through a small plastic straw, then swoosh it around inside the frame to cover the interior.

https://cimg3.ibsrv.net/gimg/bikefor...674c4855d3.jpg