Black marking – permanent, deep-black, and corrosion-resistant markings
Black marking is a procedure in laser processing which causes extremely dark, high-contrast markings on a surface without material ablation. Extremely short laser pulses cause structures on the surface at the nanometer level. The rough surface ensures that light scattering is reduced, and creates a marking with constant depth and a consistent black colour. If the laser pulses used for this marking are ultra short, this means that the color change in specific parameter ranges is also corrosion resistant. The reason for this is that the use of ultrashort pulse lasers means that the heat-affected zone is extremely small, meaning that enough free chrome remains on the surface that a self-healing oxide film can form.