Study On Corrosion Behaviors Of Mild Steel And Stainless Steel In Ethanethiol/Ethanol Solution

The amount of imported crude oil is increasing annually. This led tomore and more serious sulfur corrosion of storage devices andprocessing facilities in petrochemical enterprises. The control of sulfurcontent is becoming increasingly difficult. Mercaptan is extensivelydistributed in the light fractions of crude oil. Although the amount ofmercaptan is small relative to the total amount of crude oil, the dangerof mercaptan is big.In our work, we have studied the corrosion behaviors of Q235mildsteel,304stainless steel and316L stainless steel in conditions of variedtime, ethyl mercaptan concentration and temperature inethanethiol/ethanol solution by using weight loss measurement,potentiodynamic polarization and electrochemical impedancemeasurements. The morphology of the mild steel was observed byusing SEM. The products of Q235mild steel was characterized andanalyzed by using XRD, XPS and IR. The mechanism of anodic andcathodic was also discussed.Our results showed that that the corrosion rates increased withincreasing ethyl mercaptan for Q235mild steel,304and316L stainlesssteel. The addition of ethanethiol did not affect anodic reactionmechanism. The increasing corrosion rates was because ethylmercaptan could react with the anodic product—ferrous iron—to formsecondary products which would also accelerate anodic process. IRresults showed that there were C-C stretching vibration peak, C-Hbending vibration peak,-CH3and–CH2-characteristic adsorption peakin the spectrum. This indicated that there was CH3CH2S-in the products molecular. Ferrous mercaptan would be oxidated to S, FeO and Fe3O4when exposed to the air. XRD results of Q235corrosion productsshowed proved that there was Fe3O4, FeO and S, the corrosion ratesincreased with increasing ethyl mercaptan. XPS results showed that thechemical valences of Fe in the corrosion products are+2and+3. Thechemical valences of S are-2and+6.Our research received the corrosion behaviors and influence rule ofinfluencing factor in ethanethiol-ethanol solution. The mechanism ofcorrosion reaction was analyzed. This will give a helpful reference tocorrosion protection method and petrochemical material selection.