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Infrared and Ultraviolet-Visible Reflection Spectra of the Surface Films on Copper Treated with Benzotriazole

1971; Japan Institute of Metals and Materials; Volume: 35; Issue: 12 Linguagem: Inglês

10.2320/jinstmet1952.35.12_1165

1880-6880

N. Morito, Wataru Su euml taka,

Electrodeposition and Electroless Coatings

For a better understanding of the corrosion inhibition mechanism, it should be quite profitable to know the structure of the films of adsorbed inhibitor molecules or the surface reaction films on metals. We studied the infrared (4000∼400 cm−1) and the ultraviolet-visible (50000∼12500 cm−1) reflection spectra of the surface films on copper treated with benzotriazole; the most potential inhibitor of copper. The surface film on evaporated copper was formed by immersing for 20 hours in 3%NaCl aqueous solution (pH 3, 25°C) containing 0.02 M benzotriazole (BTA).The infrared high sensitivity reflection spectra of the surface films on copper, in which the absorption band due to N-H stretching vibration disappeared and that of N=N stretching vibration shifted to a lower wavenumber, indicate that the film consists of benzotriazole-cuprous salt(BTA-Cu(I)) formed by the substitution of hydrogen atom in the NH group with Cu(I)ion. The relative intensity of the absorption bands of C-H stretching and C-H out of plane deformation vibration shows that C-H stretching vibration, i.e., the plane of BTA-Cu(I) molecule is parallel to the copper surface. Far-infrared reflection spectra (400∼200 cm−1) suggests the presence of N-Cu-N deformation vibration and the surface film BTA-Cu(I) may be a polymer.The electronic reflection spectra of the copper surface immersed for 150 sec are in near agreement with the spectra of BTA-Cu(I). The spectra of very thin films (<10 Å) are a little different from that of BTA-Cu(I), but are quite different from that of benzotriazole-cupric salt (BTA-Cu(II)) and BTA. Therefore, the thin surface film seems to be composed of a similar compound to BTA-Cu(I).