Copper corrosion protection in neutral media by dicarboxylic acid salts

• Yu.I. Kuznetsov, I.А. Kuznetsov and D.B. Vershok

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

Abstract: Sodium succinate and a mixture of alkenylsuccinic sodium salts with the number of carbon atoms in the alkenyl n_c = 12–15 (SKAP-25) were studied as copper corrosion inhibitors (CI). It was shown that sodium succinate, despite the high hydrophilicity of its anion, can be an inhibitor of copper anodic dissolution in borate buffer (pH 7.4) containing 10 mmol NaCl. It decreases the value of passivation current density i_p and increases the potential of local depassivation E_ld. More hydrophobic succinate derivatives, SKAP-25, even more clearly show the properties of copper CI, decreasing i_p and significantly increasing E_ld in the same solution at lower concentrations, C_in ≥ 0.17 mmol/L. However, comparison of copper anodic polarization curves obtained in a solution of more hydrophobic sodium tridecanoate (n_c = 12) and SKAP-25 showed better alkylcarboxylate efficiency in stabilizing the passive state of copper. In this regard, the SKAP-25 anions are closer to the anions of the known CI, sodium oleate, which also contains a double bond. The efficiency of copper passivation by aqueous solutions of SKAP-25, sodium oleate and sodium tridecanoate in a humid atmosphere with daily condensation of moisture on the samples is compared. In the case where corrosive chlorides are absent, treatment with SKAP-25 turned out to be more effective. However, if after copper passivation, samples were immersed for 10 s in water containing 1 g/L NaCl, the protective properties of SKAP-25 became weaker than those of sodium tridecanoate. In order to enhance copper protection by SKAP-25 anions in the presence of chlorides, we studied the behavior of copper by electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution, without and with addition of SKAP-25 and 2-mercaptobenzothiazole sodium salt (S2-MBT) whose protective effect is due to the formation of a sparingly soluble complex with Cu(I). It was shown that very small additives of S2-MBT sharply enhanced the protective effect of SKAP-25, moreover, a blend of these CIs can be more effective than S2-MBT itself, which is poorly soluble in neutral media. The efficiency criterion is the S2-MBT coating resistance value, which is calculated from the selected equivalent electrical circuit.

Keywords: copper corrosion, copper protection, carboxylic acids, dicarboxylic acids, EIS, copper corrosion inhibitors, electrochemistry

Int. J. Corros. Scale Inhib., 2019, 8, no. 4, 1022-1034 PDF (922 K)
doi: 10.17675/2305-6894-2019-8-4-13

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