Synergistic mechanism of nitrogen addition and dissolution on the corrosion behavior of diamond-like‑carbon films on HP13Cr stainless steel surface

Abstract

Synergistic mechanisms of nitrogen addition and dissolution on the corrosion resistance and long-term protection behavior of diamond-like carbon (DLC) films prepared by plasma-enhanced chemical vapor deposition on the surface of HP13Cr stainless steel have been investigated. It was found that both nitrogen addition (at nitrogen flow rates of 0 sccm, 5 sccm and 10 sccm) and nitrogen dissolution during exposure in NaCl solution had significant effects on the corrosion behavior of the DLC films. More CN and N=C=N bonds were formed, and the size and amount of the defects in the DLC films were significantly reduced as the amount of nitrogen increased. The current density of the DLC film with 5 sccm nitrogen addition is 6.46 × 10−9 A/cm−2, which was reduced by one order of magnitude compared with the film without the addition of nitrogen. However, the current density of the DLC film with 10 sccm nitrogen addition is increased to 1.37 × 10−6 A/cm−2 when excessive nitrogen was added. When exposed for a long time, the expansion of the pores within the film was suppressed because the dissolution of nitrogen can effectively reduce the degree of acidification of the electrolyte within the pores. The DLC film with the nitrogen addition of 10 sccm had the best long-term service protective effect on the HP13Cr in the present work. The influencing mechanisms of different amounts of nitrogen on the corrosion behavior of the DLC films are also discussed.