Structure and properties of protective oleic acid films on magnesium formed upon contact treatment and chamber treatment

• A.Yu. Luchkin, V.A. Luchkina, I.A. Kuznetsov, A.A. Chirkunov, O.A. Goncharova, Yu.I. Kuznetsov, S.S. Vesely and N.N. Andreev

A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky pr. 31, 119071 Moscow, Russian Federation

Abstract: The structure and properties of protective layers formed by oleic acid (OA) upon contact and chamber treatment of magnesium have been studied by a set of corrosion, electrochemical and physical methods. It has been found that treatment of magnesium in an OA solution in isopropyl alcohol and in hot OA vapors (chamber treatment, CT) results in an increase in metal corrosion resistance and inhibition of its anodic dissolution. CT is more efficient than contact treatment. In both variants of magnesium treatment, OA forms protective surface films with approximately the same thickness, which however have different structures. When magnesium is immersed in an OA solution, rounded agglomerates almost merging with each other are formed on its surface. In the case of CT, the surface films have a reticulated structure. The protective effect of OA is associated with magnesium passivation. However, in the case of CT, passive films are characterized by larger pitting potentials and anti-pitting basis in chloride-containing electrolytes. Both variants of magnesium corrosion inhibition are characterized by a mixed blocking–activation mechanism. The activation mechanism predominates in the case of CT.

Keywords: magnesium, oleic acid, gas-steam treatment, corrosion inhibitor, AFM, EIS

Int. J. Corros. Scale Inhib., 2023, 12, no. 4, 1703-1718
doi: 10.17675/2305-6894-2023-12-4-16

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