I’ve found that once you get a spot on stainless steel that starts to rust it’ll keep coming back, even after you clean and polish it. So on our stanchions I’ve just been repolishing with Brightboy every 4 months or so which was frustrating not to mention time consuming.
When I mentioned this to a friend he recommended re-passivating the stainless using Wichinox. I haven’t tried it long enough to know how well it’s working but in theory it should re-passivate the steel which will stop it from rusting for a good long while.