Next job, remove the bottom bracket bearing, as the powder coat curing will not do any good to it, but also it's knackered anyway!
I hate the splined bearings. There is so little depth for the tool to mate and the socket tools have such an offset, that there is a high chance if it slipping, if the bearing cups are siezed.
And guess, what? They were rusted on solid. I had to check the direction I was turning them as there was no movement and Bromptons are notorious for being weird! All the YouTube videos stated the same, i.e. standard BSA, except one, which claimed BSA threads are the opposite of reality! In the end I took a magnifier to the tiny amount of exposed thread on the non drive side. Sure enough, it's standard BSA thread.
As it just wouldn't move without risk of the tool jumping out, I worked out a nice technigue in the end. I used a big G clamp between the tool on one side and the end of the crank shaft on the other. I could put as much force as I wanted on it and it took me jumping on the spanner on one side and the other, I had to use a 1m tube over the spanner.
I must admit that I completely wrecked the drive side by attempting to undo it with the vice. I didn't realise that it pressed the splines inwards, so the tool didn't fit and slipped anyway. I got the spline tool to fit using a big old vice instead of the G clamp.
I was so relieved that the G clamp method worked. I saw another nice technique for one of the flat tools from people like Park Tools, using a cup bolted onto the crank shaft, which pushes the tool against the splines. Something like an old blunt hole saw could do for that.
Once off, the old BB looks horrible. It's pretty obvious that the aluminium against steel has corroded the steel, presumably helped by salt water penetration in the Winter. Luckily I have a BB thread tool. I will clean everything up, but won't rethread until I've powder coated. I might used the old BB shells to stop powder ingress, but I need to be carefull they don't get too coated too, as the coating could chip off when I remove them.
I'll check with the owner, but Hollowtech bearings and crank would be a nice upgrade.
Now all I need to do is grind, sand or file off any more loose paint, flatten the rest, then clean it all down ready for powder coating at last!