Chemical, electrochemical and tribological study of various olive oils and their behaviour on steel

Abstract

The influence of different chemical composition and physical properties of olive oils, produced from various districts in Morocco with various acidic numbers (from 1.76 to 18.01), on their tribological performance and corrosion protection has been investigated. The chemical composition was determined by means of IR, ¹H and ¹³C NMR spectroscopy. The investigated olive oils show small quantitative and qualitative differences between each other (the amount of free fatty acids and the composition of fatty acids in triglycerides). The spectroscopic data let us unambiguously determine in general that the main fatty acids in oils are saturated palmitic and/or stearic acids, unsaturated oleic and linoleic acids except linolenic acid. The oxidation stability of oils was estimated. The contact angle measurements and electrochemical impedance spectroscopy data show that all films of olive oils on the surfaces of steels are porous; therefore, the values of corrosion inhibition efficiency are relatively low and ranged from 57 to 75%. The variations of friction coefficients and their mean values, the wear of steel covered by olive oils were estimated. The oils with the highest oxidation stability also show better lubricating properties.