Based on the Honshu Karambit.
The knife was masked to protect the handle. The knife is sandblasted to create better adhesion. Then the surface is cleaned using metal prep which helps the paint adhere. Then a self-etching primer is applied that eats into the metal a little bit to get a strong bond. Black paint is applied, and an airbrush is used to paint a space scene. Finally, a clear coat of Imron is applied. Imron is a durable clear coat used on NASCAR. The clear coat will resist most minor scratches, but scratching hard objects like rocks or metal can damage the paint.