Molecular structure and efficiency of triazole derivates and other heterocyclics as Corrosion inhibitors for copper

Abstract

Dedicated to Professor Dr. Alfred Rahmel on the occasion of his 60th birthdayThe inhibition of copper corrosion by various triazole derivates, benzotriazole (BT) and other heterocyclic compounds is investigated to reveal the relation between molecular structure and inhibition efficiency. Measurements of weight loss yield the protection factor S depending on inhibitor concentration c, potential E , pH and temperature T. Current potential curves i(E) show that various processes are inhibited, for example the oxygen reduction or the anodic copper oxidation. Capacity measurements and XPS analysis, prove the formation of protective layers, the stability of which determines the applicability of the inhibitor under varying conditions. The influence of molecular structure is explained on the basis of electrochemical and surface analytical measurements. 3-Amino-5-alkyl-l,2,4-triazoles (AAT) are the best inhibitors in the whole pH range since they can form molecular compound layers in neutral and alkaline solutions but heteropolar-compound layer in acid solutions. An intermediate aliphatic chain length gives the best efficiency since it allows sufficient solubility on the one hand and an effective hydrophobicity of the inhibitor layer on the other. The influence of similar heterocyclic compounds is tested but they have much smaller efficiencies. Benzotriazole is comparable in neutral and weak alkaline solutions but it is less effective in acid solutions and fails at high temperatures.Die Inhibition der Kupfer-Korrosion durch verschiedene Triazolderivate, Benzotriazol (BT) und andere Heterocyclen wurde untersucht, urn einen Zusammenhang zwischen der Molekulstruktur und der Inhibitionswirkung zu erhalten. Gewichtsverlustmessungen ergeben einen Schutzfaktor S, der von der Inhibitorkonzentration c, dem Potential E, dem pH-Wert und der Temperatur T abhangt. Potentiodynamische StrodSpannungs-Kurven zeigen, daR verschiedene Teilreaktionen, 2. B. Sauerstoffreduktion oder Kupferauflosung, inhibiert werden. Kapazitatsmessungen und XPS-Untersuchungen beweisen die Bildung von Schutzschichten, deren Stabilitat die Anwendbarkeit des Inhibitors bei unterschiedlichen Testbedingungen gewahrleistet. Der EinfluR der Molekulstruktur wird anhand von elektrochemischen und oberflachenanalytischen Messungen erlautert. 3-Amino-5-alkyl-1,2,4-triazole (AAT) sind die effektivsten Inhibitoren im gesamten pH-Bereich, da sie in neutralem und alkalischem Medium molekulare Deckschichten. in saurer Losung jedoch heteropolare Deckschichten bilden konnen. Bei einer mittleren Kettenlange des Nkylrestes wird die beste Schutzwirkung erzielt, da sowohl eine genugende Inhibitorloslichkeit als auch eine stark hydrophobe Inhibitorschicht gewahrleistet ist. Mit AAT venvandte Heterocyclen zeigen eine deutlich geringere Inhibitionswirkung. BT ist in neutralen und schwach alkalischen Losungen vergleichbar, jedoch in saurem Medium und insbesondere bei hoheren Temperaturen wesentlich weniger wirksam.

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Investigating metal‐inhibitor interaction with EQCM and SVET: 3‐amino‐1,2,4‐triazole on Au, Cu and Au–Cu galvanic coupling

“…Organic inhibitors are compounds that applied in very small concentrations are capable of effectively reduce the corrosion rate. Among these compounds those belonging to the group of azoles, which contain nitrogen and/or sulphur, are considered to be effective corrosion inhibitors for copper in a wide range of aggressive environments …”

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