Tough black finish for spring steel?

I'm looking for a reasonably wear and corrosion-resistant black finish for a carbon steel spring part. This'll be a fairly small initial production run.

TiN obviously wears excellently, but corrosion is still an issue. I'm looking into electroless nickel. It seems some formulations result in a dark grey/black finish?

Any ideas or suggestions would be great...

What do you mean by "reasonable"? It will be difficult to recommend something without more specifics.

You could use electroless nickel, then an oil rubbed, black nickel plate, but it won't wear like TiN.

Have you considered Molten Salt Bath Nitriding? This process does not do much as far as hardening, but it gives excellent corrosion resistance as well as increased wear resistance and lubricity. I am not an expert in this area, however I have a customer who does this process for an appliance motor manufacturer.