Can you use black coated knife with magnesium sticks to make a fire?

No. A magnesium fire starter works as a flint and steel. When you scrape the magnesium with the steel, it produces a spark that ignites the tinder. Steel refers to the type of metal used to create the spark, as opposed to specific items like knives.

In principle, any hard object can be used to create enough friction and heat to ignite magnesium - like a rock or a knife. However, a regular knife isn't specifically designed for this purpose. It is unlikely to produce a consistent or sufficient spark to reliably start a fire.

Additionally, using a black coated knife may further decrease its effectiveness for making fire with magnesium. The black coating can create a barrier between the magnesium and the steel, preventing good contact and reducing spark production.