decorative finishing. how to blacken steel/SS AND laser engrave w/o getting rust

[Stirling]

Im making some SS and carbon steel products. the carbon steel products need to be coated (grey or black) and then fiber laser engraved for data.

is there any way to get a nice engraving that does not destroy the coating and then rust? ive been hot phosphating them but the customer now wants engraving.
i can deep engrave and then phosphate, but a opposing color/sharp image would be prefered. im just not seeing a solution in my head.

for the SS, whats a good way to blacken? (preferably something that can be done on a small/cheapish scale, $5000 and under initial setup for small handheld parts)
i considered sandblasting/laser engraving to a nice black with the graphics remaining the sangblasted SS but the laser polishes the steel as it blackens (surface aneeals is) i want the matte effect of sandblasting to remain (more laser testing to go. maybe its acheavable but i doubt it

i often laser engrave anodized aluminum products and boy, what a nice result, the laser bleaches the dye and the coating is left, stunning white results.

 

[MaxPrairie]

Black oxide or black electroless nickel come to mind. Black EN will be darker as the nickel gets thicker. May be able to laser and still have nickel underneath on steel parts.

 

[Nerdlinger]

I’m pretty sure the fiber laser will/can passivate the surface when marking so it will not react with the moisture in the air and oxidize. So maybe look into that. Good luck!

 

[Halcyon]

I’m pretty sure the fiber laser will/can passivate the surface when marking so it will not react with the moisture in the air and oxidize. So maybe look into that. Good luck!

It forms a nitride, if I'm not mistaken.

Less durable, but you could consider a printing process like silkscreening.

Maybe ask your plater if it's possible to do a layer of black nickel over silver nickel, then find laser settings that only penetrate the top layer. I worked with some graphical substrates where it was basically powdercoat over anodizing, and worked on a very small ~40w co2 laser.

 

[Orange Vise]

Stainless steel can be black oxided but requires a different chemical bath.