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

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Abstract
The 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 ε, pH and temperature T. Current potential curves i(ε) 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‐1,2,4‐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.

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