Though a large literature exists on thermal spray coating, there have been few attempts to directly observe molten droplets as they land on a solid substrate, freeze, and coalesce to build up a coating. This paper aims to photograph the impact of small tin droplets (200-600 micrometer diameter) landing with high velocity (20-50m/s) on stainless steel surfaces to form a coating. The substrate temperature and roughness are varied and the deposition efficiency (the fraction of the coating material which adheres to the surface) for different values of surface roughness and temperature are measured. A molten metal droplet generator is used to generate tin droplets of the desired size. To achieve high impact velocities, the substrate is mounted on a rotating flywheel. By controlling the time at which a droplet was ejected, it is ensured that the moving substrate hit the airborne droplet with high velocity and photographed the impacting droplet. Paper includes a German-language abstract.