Black metals are metals with a sponge-like nanoporous surface. Their surface appears black because light enters the pores and does not exit back due to multiple reflections. Black metals can be used as heat-absorbing coatings in thermal detectors or pyroelectric devices. In this research, 500 nm and 1000 nm thick black aluminium (B-Al) films were deposited on 1 mm thick fused silica substrates using pulsed DC magnetron sputtering in a mixed atmosphere of argon and nitrogen of 94% and 6% respectively. The resulting B-Al films had a soft surface which was easily susceptible to scratching. It was found that aluminium nanowires grew from scratches and small abrasions on the film surface when the films were annealed in the vacuum of 10-3 Pa at a substrate temperature of 350 °C. Energy-dispersive X-ray analysis confirmed that the atomic percentage of aluminium was 70–80% both in the film and the nanowires, and the remaining elements were carbon, nitrogen, and oxygen. Longer nanowires grew in the case of a thicker film. Some nanowires had a spiral shape that suggested that their growth was driven by a screw-dislocation mechanism. Scanning electron microscopy did not reveal any visual changes in the shapes of mechanically intact pores after annealing of the B-Al films.