Inhibition of metal corrosion in neutral aqueous solutions by succinic acid salts

• Yu.I. Kuznetsov, N.P. Andreeva and M.O. Agafonkina

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

Abstract: The adsorption, protective and passivating effect of sodium succinate and a blend of sodium alkenylsuccinates SKAP-25 on the oxidized surface of copper, copper-nickel alloy MNZh5-1 and low-carbon steel St3 in a neutral chloride solution were studied. The free adsorption energy (–ΔG⁰_a,max) values for all studied metals suggest chemisorption interaction of these organic anion with oxidized metals surfaces: (–ΔG⁰_a,max) for St3 60.2 kJ/mol, for copper 77.4 kJ/mol and for copper alloy 89.3 kJ/mol. Sodium succinate is able to stabilize the passive state of the MNZh5-1 alloy in a neutral chloride buffer solution. On copper, copper alloy and St3, protection against local depassivation is observed up to a certain concentration, above which the protective properties of sodium succinate decrease. Polarization measurements on the air-oxidized surface of low-carbon steel St3 showed that sodium succinate and SKAP-25, as well as their compositions with 2-mercaptobenzothiazole (2-MBT), are able to reduce anodic dissolution currents and increase the local depassivation potential. Corrosion tests of St3 in a 0.01 M NaCl solution proved the advantage of using the composition of SKAP-25 with 2-MBT (7.1:1) in comparison with the individual compound: the degree of protection of St3 at C_inh=7 mmol/L is 99%, and sodium succinate+SKAP-25 (1:1) at C_inh=7 mmol/L is Z=93%.

Keywords: corrosion inhibitors, copper, copper alloy, nickel, low-carbon steel, adsorption, ellipsometry, Temkin isotherm, succinic acid, SKAP-25, mercaptobenzothiazole

Int. J. Corros. Scale Inhib., 2024, 13, no. 2, 1322-1336
doi: 10.17675/2305-6894-2024-13-2-36

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