I have a 6 year old Surly Crosscheck bike in hospital green. It began to speckle with small rust spots through the paintwork this year. The insides are fine. I keep this (main) bike in a secure (Trimetal) outside storage along with 2 other bikes. They show no problems even though one, a Hetchins, is now nearly 40 years old. I do look after my bikes pretty well.
Why should a decent chrome alloy frame do this, and has anyone else had similar problems with a Surly?