On painted steel the laser works the paint, not the metal: it removes the coating to reveal bright steel underneath. This is the one case where a blue diode gives a crisp result on metal.
Settings: what really matters
The goal is to remove paint without heating the steel: medium power, high speed, single pass. A second pass does not make the line clearer, it widens the area where paint blisters around the design.
Contrast depends on the paint: matt black lacquer gives a very visible mark, pale or metallic paint much less.
A fibre source goes through the paint and then marks the metal: deeper, but less contrasted than a clean diode strip-back.
Risks and finishing
You do not know what an industrial paint contains: some primers and powders give off frankly toxic fumes. Serious extraction, and avoid painted parts of unknown origin.
The bared steel is no longer protected: on an exposed part it will rust. Clear spray lacquer over the mark solves it.
A dry cloth is enough afterwards: avoid solvents that would attack the paint around the design.
Every figure on LaserSettings comes with the machine, the laser source, the material and the thickness it was tested on. A setting published for a 10 W diode says nothing about a 40 W CO2, and a setting for 3 mm says nothing about 6 mm: check those four things before you copy any number.
Settings are confirmed or disputed by the members who reproduce them, so reliability comes from cross-checking rather than popularity. Photos of the result — cut edges, engraving shades, scorching — tell you more than a single number found on a forum.
Whatever the material, treat a published setting as a starting point: run a small power/speed test grid on an offcut, clean the lens, redo the focus, work with fume extraction and air assist, wear glasses rated for your wavelength and never leave the machine unattended.