Quinine sulfate: a pharmaceutical product as effective corrosion inhibitor for carbon steel in hydrochloric acid solution

作者：Samide Adriana^*; Tutunaru Bogdan

来源：CENTRAL EUROPEAN JOURNAL OF CHEMISTRY, 2014, 12(9): 901-908.

DOI：10.2478/s11532-013-0399-9

• Quinine sulfate
• Corrosion inhibition
• Carbon steel
• Electrochemical measurements
• Adsorption

Quinine sulfate dihydrate (QNS), IUPAC name: (8S,9R)-6-methoxy-4-quinolenyl-5-vinyl-2-quinuclidinyl methanol sulfate dihydrate, was tested as corrosion inhibitor for carbon steel in 1.5 mol L-1 HCl solution using the potentiodynamic polarization and the electrochemical impedance spectroscopy (EIS) associated with UV-Vis spectrophotometry. The electrochemical results showed that, the inhibition efficiency (IE) increased with the increase in QNS concentration, reaching a maximum value of 93.35 +/- 0.25%. The polarization resistance (R (p)) followed the same trend, obtaining the highest value of 659.7 Omega cm(2), while the corrosion current density (i (corr)) reached the lowest level of 195 A mu A cm(-2). The action mechanism of QNS was proposed considering the ability of quinine (QN) to be adsorbed on the metal surface via the lone pairs of electrons from hydroxyl oxygen atom, and/or from quinoline and quinuclidinic nitrogens. The occurrence of the complexes between inhibitor and iron ions was considered an additional process, which may contribute to protective layer formation. The Temkin adsorption isotherm was found as the best fitting for the degree of surface coverage (theta) values. In order to elucidate the mechanism of protective layer formation, the free energy of adsorption (Delta G (o) (ads)) value was calculated. This indicates that the inhibitor acts by chemical adsorption on the steel surface.

• 出版日期2014-9