Abstract: Carbon nanofiber (CNF) coatings were successfully deposited on a low carbon steel substrate that was pretreated by concentrated nitric acid using an oxyacetylene reducing flame. The morphologies and the microstructures of the CNF coatings were characterized using scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. The CNFs were compact, entangled with each other, and highly graphitized with diameters from 80 to 100nm and lengths from 3 to 5μm. They tended peel off the substrate because of a weak adhesion strength. Iron oxide particles were produced on the pretreated low carbon steel substrate surface in the flame, and these acted as growth catalysts for the CNFs.