We report on UDI laser marking of 13 medical steel grades using industrial-grade and commercially available laser systems delivering short (ns) and ultrashort (ps, fs) laser pulses. Marking with ultrashort pulses is well-known as medical black-marking and leads to excellent contrast with view-angle-independent readability. Black-marking, however, comes along with micro-structuring of the surface.

Here we studied the impact of micro-structuring on long-term legibility, cleanability and cytotoxicity. Cleanability tests have been performed using BCA analysis according to FDA regulation ASTM F2459-18.

In addition, best-effort laser parameters are presented for ns, ps and fs pulse durations which fulfill the stringent UDI marking requirements like corrosion-resistivity and long-term legibility even after numerous reprocessing cycles (chemical reconditioning followed by autoclaving). Such tests have been performed on surface-treated samples ranging from electro-polishing, slide grinding, glass bead blasting to sand blasting and tumbling.

Finally, in order to match the different passivation strategies established in industry the samples have been undergone different sets of passivation treatment before and after marking, in accordance with regulation ASTM 967/A.

In conclusion we present a comprehensive study on laser marking of medical steel grades with different pulse durations, numerous surface finishes and passivation treatments and report best-effort results for long-term corrosion-free marking.