Adsorption of depocolin and inhibition of copper dissolution in aqueous solutions

Abstract

The work is devoted to a study of an interesting representative macrocycle compound-3,7,12,17-tetramethyl-8,13-divinyl-2,18-deuteroporphyrin (depocolin) containing two peripheral carboxylic groups. The inhibiting action and adsorption on copper in neutral borate buffered solutions depending on depocolin concentration were studied. Using electrochemical curves, the influence of the inhibitor on the behavior of copper in solution was determined. It was shown that at depocolin concentrations above 0.25 mmol/l, stabilization of the passive state of copper in neutral chloride solutions (рН 7.4) was observed, which was also confirmed by corrosion tests. The method of X-ray photoelectron spectroscopy was used to determine the composition and thickness of surface films. It was deduced from XPS analysis that depocolin is bonded to copper cations through two donor atoms of oxygen of the carboxyl groups. The nitrogen atoms do not participate in the formation of coordination bonds with copper cations. The calculated thickness of the adsorbed depocolin layer is proved to be 1.2 nm corresponding to the fixation of the molecule plane at an angle of 55° to the copper surface. Treatment of a sample in an ultrasonic bath did not remove the depocolin layer, which is an indication of the chemisorption character of bonding of the latter with copper. The inhibiting capability of depocolin was studied in a chamber with periodic moisture condensation and in a chamber with neutral salt fog. The samples modified with depocolin showed a higher corrosion resistance.