I want to make some edm machine tooling...

The traditional method is to use stainless steel. Due to the rising cost of stainless, I am wondering if there are any alternative (cheaper) metals, or possibly some rust proof coatings I could use on regular steel?

Hammerite do excellent rust proof paint. You can even apply it on rusty metal- I did my comprtessor tank in it :)

You could have any ferrous metal liquid nitrided or even a phosphate, that would prevent rust.

Is there any other reason that they are made from SS?

Thanks for the lead, I will check it out. No only stainless for the rust proofing...

Maybe anodizing aluminium would work, I don't know if aluminium will work or not.