Rapid fabrication of diamond-like carbon coating with excellent corrosion resistance by low-voltage plasma electrolytic deposition

Diamond-like carbon (DLC) coatings were rapidly synthesized on the surface of AISI 304 austenitic stainless steel by utilizing a low-voltage plasma electrolytic deposition (PED) method with an acetonitrile solution. The results show that, as the deposition time increases, the intensity ratio of the D and G peaks (I_D/I_G) in Raman spectroscopy initially rises and then subsequently declines, the lowest value of which is 1.17 for the coating deposited at 260 V for 60 min, and X-ray photoelectron spectroscopy (XPS) analysis indicates that the sp³-C content of which achieves to 63.63 %. As for the coating deposited at 260 V for 60 min with the thickness of 2.4 μm demonstrates a superior corrosion resistance in 3.5 wt.% NaCl solution, comparison to the untreated stainless steel, the corrosion potential of which increases from -0.540 V to -0.418 V, the corrosion current density decreases from 9.294 × 10^–6 A/cm² to 3.603 × 10^–6 A/cm², and the polarization resistance rises from 5375 Ω·cm² to 12,181 Ω·cm². The present DLC coating with excellent corrosion resistance will be suitable for corrosion protection of metallic materials in marine environments. Analysis of the corrosion mechanisms reveals that coatings with a higher sp³-C content exhibit lower electrical conductivity, which restricts electron transport within the coating surface. Therefore, the DLC coating with a higher sp³/sp² ratio displays superior corrosion resistance.