Sounds like it's been anodised. Not uncommon. Some anodising is very good, some not.
If it was me, I would see how it goes. It's a simple thing to remove. Give it a winter, look at it in the spring. If it's rusty, rub it down a tadge and take it to the galvinisers.
I was given a saw bench a few years ago, with a chainsaw mount. It's really useful, but I keep it outside year round, just greasing up the moving parts. the PO did the same. It's anodised, not galvinised. I recon it's been outside twenty years. Rust is just starting to show, so in a couple of years, I'll either pain it or get it galvanised.