Adsorbtion of sodium tridecanoate on copper from aqueous solutions and copper protection from atmospheric corrosion

Abstract

The adsorption and protective effect of sodium tridecanoate CH₃(CH₂)₁₁COONa (NaC 13) on copper and the possibility of increasing the effectiveness of protection by joint use with a trialkoxysilane (TAS) were investigated. A set of electrochemical, ellipsometric and corrosion tests was carried out on samples of M1 copper (copper content > 99.9%). From an analysis of the anodic polarization curves of copper from solutions containing NaC 13 , it follows that when the inhibitor concentration is >0.07 mmol/l, the current density of copper active dissolution decreases and spontaneous passivation of the electrode occurs with a shift in the value of the pitting potential E pit in the positive direction. With an increase in the concentration of the inhibitor, the value of E pit increases while the anodic current density decreases. When the concentration of the inhibitor in the solution is 1.6 mmol/l or more, the value of E pit shifts to the oxygen evolution region. Studies of NaC 13 using the ellipsometric method showed that the adsorption of the inhibitor starts at very low concentrations, viz., 0.01 nmol/l. Adsorption is described by the Temkin equation with an adsorption free energy of 67 kJ/mol. In comparison with sodium oleyl sarcosinate СН 3 (СН 2) 7 СН=СН(СН 2) 7 СОN(CH 3)СН 2 СООNa (SOS) and sodium laurate CH3(CH2)10COONa (NaC 12), adsorption begins at lower concentrations. Sodium tridecanoate adsorption on copper is polymolecular. Accelerated corrosion tests with daily moisture condensation on copper pretreated with an inhibitor solution at 60°C for 5 minutes were carried out. It was shown a protective mixture of NaC 13 and TAS significantly increased the time until the appearance of the first corrosion site.

Copper corrosion protection in neutral media by dicarboxylic acid salts

“…The presence of a double bond in these dicarboxylic acids also reduces their hydrophobicity, as indirectly indicated by a comparison of stearic and oleic acids (Table 1). According to the results of copper polarization measurements obtained in [23] in the same borate buffer containing 10 mmol/L NaCl, the shift of E ld to 0.96 V in the presence of sodium oleate occurs at C in = 3.1 mmol/L. Therefore, despite the significantly higher hydrophobicity of the anion of oleic acid compared to those of the alkenylsuccinic acids contained in KAP-25, the effectiveness of these CIs is similar.…”

“…With an increase in C in , an improvement in the protective properties is noticeable: E ld monotonically increases and reaches the value of the oxygen evolution potential at 7 mmol/L. However, when compared with the polarization curves obtained for sodium tridecanoate, i.e., an alkylcarboxylic acid salt with an alkyl length of n c = 12 (for KAP-25, the alkylene chain has n c = 12-15), it is clear that the monobasic acid salt shows the best result here: addition of C in = 3.5 mmol/L to SKAP-25 is needed for shifting E ld to 1.0 V, against 0.70 mmol/L in case of tridecanoate [23]. Apparently, this is due to the fact that the monobasic acid has a greater hydrophobicity (log D = 2.97) than KAP-25 acids that have one more carboxy group, which dissociates in solution to give log D = -0.25 to 1.61 (Table 1).…”

“…The results of these tests, in which the corrosiveness of the medium was created only by daily condensation of moisture on samples pre-treated by immersing them for 5 min in hot (60°C) CI solutions at C in = 8 or 16 mmol/L, are presented in Table 2. For comparison, it also presents the results of similar tests of such well-known carboxylate-type CIs as sodium tridecanoate [23] and sodium oleate [11].…”

Thin Protective Coatings on Metals Formed by Organic Corrosion Inhibitors in Neutral Media

“…The adsorption of mono-and dicarboxylates on Cu was extensively studied by in situ reflectance ellipsometry. Adsorption measurements were performed in borate buffer with pH 7.4 on passive Cu after reduction of the electrode surface at E = -0.60 V followed by its oxidation for 30-40 min at E = 0.0 V. It has been shown that adsorption is sometimes adequately described by the Frumkin isotherm equation [78], but more often by the Temkin equation [32,[79][80][81][82] and increases with the chain length of their molecules. Thus, in [78] five monocarboxylates were studied whose inhibition efficiency against local anodic dissolution of Cu increased in the same order as the hydrophobicity of the corresponding acid anions (logD): SMeF (2.29) < SFF (2.57) < SPhU (3.68) < SOl (5.10) < SOS (5.65).…”

“…Sodium tridecanoate CH3(CH2)11COONa (NaC13) is sufficiently soluble in water to be an efficient passivator of Cu in it [79]. Its adsorption starts at low Cin = 0.01 nmol/L, with Comparison of the protective efficiency of a Cu thin coating formed in 2.0 mmol/L BTA solution with similar passivation by SOS or SOl was carried out in a humid atmosphere with daily condensation of moisture on the samples.…”