Polishing running boards.

Not sure if this is the right section, but I was just about to use some polish and decided to hold off and ask first. I have an MDX with black running boards. I presume they're aluminum, painted/anodized/powder-coated. They have some hard water spots on them I'd like to get off. They won't wash off with other methods. Would the polish be ok on these?
Thanks

 

I assume these running boards would handle a metal polish just fine....i use never dull when they get cloudy after i wash, but for an abrasive metal polish i would just do a test spot first on the underside first but i dont see any issues here...

 

Are they painted?

 

I'm not sure if they're painted, anodized, powder-coated, or what. It's kind of like a rough eggshell finish. I tried a little bit of polish on the bottom. Definitely not the way to go. Leaves a white residue.

 

Hmmm, I have to find a MDX and look for you. I would not use metal polish on them.

 

I assumed they were chrome, im sorry but at least you were smart and used a test spot!