Use of some natural oils as crude pipeline corrosion inhibitors in sodium hydroxide solutions

Galvanostatic and potentiodynamic anode polarization methods were used to study the inhibiting effect of parsley, lettuce, and radish oils on corrosion of carbon steel L-52, used in Egypt in manufacturing pipelines, in 0.5 M NaOH solution. This effect increases with an increase in the concentration of these oils, which is due to adsorption of the basic components of the oils on the surface of the steel. The adsorption process is described by a Langmuir isotherm. It was found that incorporation of chloride ions in the 0.5 M solution of NaOH accelerates pitting corrosion of the steel as a result of moving the pitting potential toward more negative values. The investigated oils added to the solutions containing chloride ions protect steel from pitting corrosion.