Corrosion Resistance Enhancement in Acidic solution for Austenitic Stainless Steel by Gas-Phase Hybrid Deposition Process

In acidic environments the corrosion rate of stainless steels is considered high, this is due to pitting occurrence in concentrated chloride environments. The Austenitic steels such as type 316 stainless steel generally not recommended for Hydrochloric acid storage in petroleum planets except when solutions are very dilute and at room temperature, otherwise pitting may occur. In this work, a multicomponent coating (Ti-B-N-C) was deposited on the austenitic stainless steels (AISI 316) that used in petroleum industry. The coating process has been achieved by mixed vapor deposition technique; this was done in attempt to improve the resistance to pitting corrosion for austenitic stainless steels surface. The structural characterization for the deposited Ti-Base coating was done by using XRD technique, and the Scanning Electron Microscopy (SEM). Electrochemical corrosion tests have been performed by using electrochemical test in 0.25M hydrochloric acid (HCl) as an aqueous solution at 22˚C to obtain the anodic polarization curves for the coated surfaces. Several interesting observations have been made During the test. As expected, the surface of the AISI 316 suffers from a sudden increase in the current density at the potential above 1500 mV due to the occurrence of pitting corrosion. In addition, the Ti-B-C-N coating surfaces show great future in reducing the current density of the steel surface in the anodic region, indicating improved pitting resistance for all Ti-based coating samples. No evidence for pitting corrosion was observed in the coated surfaces during electrochemical test even at potentials up to 2000 mV, instead, general corrosion was observed for the samples that was deposited at 750˚C since low potential values was observed for these samples .