To evaluate the effect of natural rosemary oil as non toxic inhibitor on the corrosion of steel in H3PO4 media at various temperatures.
The oil was hydro‐distilled. The oil was used as inhibitor in various corrosion tests. Gravimetric and electrochemical techniques were used to characterise the corrosion mechanism.
Chromatographic analysis by GC showed that the oil was rich in 1,8‐cineole. The oil was a good inhibitor. But, its efficiency decreased with temperature.
The inhibition efficiency increased with the concentration of the natural oil to attain 73 per cent at 10 g/l. Good agreement between the various methods explored was observed. Polarisation measurements showed that rosemary oil acted essentially as a cathodic inhibitor.
The efficiency of the oil increased with the concentration but decreased with the rise of temperature in the 298‐348 K range. The natural oil could thus be used in chemical cleaning and pickling processes.
The originality of this work is the finding of a safe and cheap inhibitor from natural plants.
