I think the problem is the contact between the AISI 2205 part and the painted (steel?) part. AISI 2205 itself is o.k. for seawater up to approx. 35 °C. But I guess the contact to the other part caused the surface corrosion.
This is an atmospheric transport situation assuming it was transported on so galvanic effects do not apply- more likely bad welding has sensitivized your 2205- you have formed chromium carbides and depleted the available chromium for corrosion protection.
How was it cut and turned?
My guess is that there is massive surface iron contamination that triggered the rusting.
The part should have been passivated in nitric acid after all machining.
Oh, by the way did the starting material have good corrosion resistance? Was it tested to A923, if not then the starting bar may not have had the optimal microstructure.
You can, because you may end up embedding a lot of iron into the surface. This will allow corrosion to start to form pits, and lead to the corrosion of the base metal.
After all machining, cutting, forming, grinding/polishing operations all SS should be passivated if you want to avoid surface corrosion.
But I will echo Stan's comment; are you positive that this is 2205?