Are you asking about paint or ????

No a oil or clear that will last and not rub rust on people's white suits.

If you ever cleaned the steel with a rasp or steel wool pad that had a high ferrous (iron) content, you imbedded the ferrous material into the steel which will cause the rust "bloom" to continue forever. This is why metal shops have completely different areas for iron and stainless steel work. You might have someone familiar with metal look at your railing to see if it has been permanently damaged leaving paint as your only option.

If on the other hand, the railings are iron not stainless, they will always have rust bloom. Only a heavy, petroleum jelly-like substance would keep them from rusting which is equally bad for clothing and yucky to touch. Again paint is the solution.

I keep adding to this, but when you paint, the surface must be sandblasted, primed and painted with a good (ie expensive) epoxy coating. And everything must be absolutely dry.

This is a new railing I'm going to be building. I don't want it to be painted. After traveling to Utah and Arizona I noticed nothing is painted and it doesn't rub rust off. Wonder what they do to prepare and preserve that raw/rusted look? All over the national parks nothing had paint( arches park and Grand Canyon)

Oil from thousands of hands.

Corten steel.

Aluminum or powder coat.

Did you figure this out? I'm curious

I ended up going with powder coating. Couldn't find a great option.