Cold rolled steel, flats or square for use as rails.

So assuming I'm going to use cold rolled flat or square for linear
rails with bearings.

I have a couple of concerns about using cold rolled, mainly with the
issue of rusting.

So,

1. If I get the cold rolled rail surface ground for tighter accuracy,
will a surface ground rail rust more quickly than a non ground rail?


2. If I was to use the same cold rolled but this time it was hardened
and ground. Would it resist the rust more?


3. How do I stop it from rusting? I can't paint it as it will have
bearings running across it.

4. Can I get the steel coated with something to stop it from rusting?
Chrome would be nice but $$$$.

5. What if I used stainless steel for a rail. Would it be okay to
use as an unmachined length, or would it need surface grinding as
well? Is it more parrallel and as straight as cold rolled steel or is
it not as straight etc?

Cheers,
Peter