Effect of fluid flow, pH and tobacco extracts concentration as organic inhibitors to corrosion characteristics of AISI 1045 steel in 3.5% NaCl environment containing CO₂ gas

Corrosion become major problem in most industries. In the oil and gas company, corrosion occurs because of reaction between steel and chemical species inside crude oil. Crude oil or nature gas provide corrosive species, such as CO₂, O₂, H₂S and so on. Fluid containing CO₂ gas causes CO₂ corrosion which attack steel as well as other corrosion phenomena. This CO₂ corrosion commonly called as sweet environment and produce FeCO₃ as corrosion products. Fluid flow factor in pipelines during the oil and gas transportation might increase the rate of corrosion itself. Inhibitor commonly use used as corrosion protection because its simplicity in usage. Nowadays, organic inhibitor become main issue in corrosion protection because of biodegradable, low cost, and environmental friendly. This research tried to use tobacco leaf extract as organic inhibitor to control corrosion in CO₂ environment. The electrolyte solution used was 3.5% NaCl at pH 4 and pH 7. Weight loss test results showed that the lowest corrosion rate was reach at 132.5 ppm inhibitor, pH 7 and rotational speed of 150 rpm with corrosion rate of 0.091 mm/y. While at pH 4, the lowest corrosion rate was found at rotational speed of 150 rpm with inhibitor concentration of 265 ppm and corrosion rate of 0.327 mm/y. FTIR results indicate the presence of nicotine functional groups on the steel surface. However, based on corrosion rate, it is believed that corrosion occurs, and FeCO₃ was soluble in electrolyte. Tobacco leaf extract inhibitors worked by a physisorption mechanism, where tobacco inhibitors formed thin layer on the steel surface.