INVESTIGATION OF COPPER ANODIC OXIDATION IN ALKALINE ELECTROLYTES WITH ALANINE BY ELLIPSOMETRIC METHOD

摘要

Copper anodic oxidation was investigated in alkaline electrolytes with alanine additives. The thicknesses of the oxidized films were determined by the ellipsometric method. Small addition of alanine (10~(-4)/10~(-3) M) increased the stability of the copper passive state and the film thickening due to an amino acid adsorption and/or the formation of stable intermediate complexes with beta-alanine on the copper surface. The passive film on copper can be partially dissolved in electrolytes with concentrations of amino acid more than 10~(-2) M and the metal exposed local corrosion as a result of the formation of soluble complexes in the electrolyte. The kinetic of alpha- and beta-alanine adsorption was investigated. It was found that in 0.01 M NaOH the beta-alanine adsorbed on the copper surface at E=-0.15 V and the mechanism of adsorption corresponds to a Frumkin isotherm of adsorption (a = 1.5 + -.05, -SIGMA G_a~0 = 30.4 + - 0.4 KJ/mol). The mechanism of the a - alanine adsorption could not be determined because of the high ability of a - alanine to complex formation.