Marking up steel

[Tatey]

I've been searching google and i cant seem to find the answer. What type of pen/or similar do steel suppliers use for writing on the steel. I have tried using sharpie markers but the pen fades after a while.

The stuff the steel suppliers use seems to last for ever, i've mainly seen it in blue and its kind of like a paint on the metal.

Any help will be much appreciated.

Cheers