2 research outputs found
Experimental characterization, machine learning analysis and computational modelling of the high effective inhibition of copper corrosion by 5-(4-pyridyl)-1,3,4-oxadiazole-2-thiol in saline environment.
An oxadiazole derivative with functional groups favouring its adsorption on copper surface,
namely 5-(4-Pyridyl)-1,3,4-oxadiazole-2-thiol, has been explored as potential inhibitor of copper
corrosion in 3.5 wt.% NaCl. Electrochemical evaluation by electrochemical impedance
spectroscopy, potentiodynamic polarization and SVET reveals inhibition efficiencies exceeding
99%. Surface microscopy inspection and spectroscopic analysis by Raman, SEM-EDX and XPS
highlight the formation of a compact barrier film responsible for long-lasting protection, that is
mainly composed of the organic molecules. Machine Learning algorithms used in combination
with Raman spectroscopy data were used successfully for the first time in corrosion studies to
allow discrimination between corroded and inhibitor-protected metal surfaces. Quantum
Chemistry calculations in aqueous solution and Molecular Dynamic studies predict a strong
interaction between copper and the thiolate group and an extensive coverage of the metal surface,
responsible for the excellent protection against corrosion
Synthesis and evaluation of anionic schiff bases as pitting corrosion inhibitor for stainless steel 304 in NaCl solution
ECS Meeting Abstracts; Volume MA2019-01The high corrosion resistance of austenitic stainless steel (SS) arises from the formation of a thin, adherent and protective passive film that forms instantaneously on the surface. Unfortunately, in the presence of aggressive ions like chloride anion, the corrosion resistance of passivated stainless steel is limited by local breakdown and pit nucleation [1]. An efficient and economical method to decrease the metal dissolution in aggressive media is the use of corrosion inhibitors. A large number of organic molecules containing electronegative functional groups, such as ¿-electron systems or heteroatoms have been proposed for the inhibition of general metallic corrosion, although the use of organic compounds as pitting corrosion inhibitors in neutral solutions is still rather limited. On the other hand, inorganic-based compounds such as chromates and nitrates are also used as pitting corrosion inhibitors for SS in aggressive media; however the application of these inorganics, especially chromates and phosphates, is not recommended because of their biological toxicity. More recently, Schiff bases have been described as cost effective inhibitors due to their robust and convenient synthesis from inexpensive precursors. They are organic compounds containing the imine (-C=N-) functional group in their structure. Schiff base derivatives with additional heteroatoms, such as N and O, and aryl groups have been used as corrosion inhibitors [2,3], but their application as pitting corrosion inhibitors has not been described.
In the present study, three new anionic Schiff bases were synthesized through by reacting para-amino benzoic acid with several aromatic aldehydes containing different functional groups in their para- site. They were designed to improve water solubility, to enhance coordination with Fe atoms by including N and O heteroatoms, two benzene rings and the imine group in their chemical structure, and to be large enough to create heavy hydrophobic complex with Fe+3.
The inhibitor efficiency of these compounds as pitting corrosion inhibitor for 304 SS in neutral 0.1 M NaCl was examined using potentiodynamic polarization measurements, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) . Polarization data show the shift of the pitting potential to more positive values with increasing inhibitor concentration. Surface analysis shows chromium enrichment at the metal surface under anodic polarization in the passive region of the metal when the inhibitor compound is present in the test solution, whereas no effect occurs under open circuit conditions. XPS data show that the inhibitor molecules do not adsorb on the clean metal, but on the passive layer instead