Ellipsometric analysis of a corrosion inhibitor in the mode of broken total internal reflection.

Abstract

Metal corrosion causes large economic losses, driving research into protection methods, among which chemical inhibitors are most common. Reliable protective coatings require high precision monitoring of thickness, optical parameters, and molecular structure of adsorbed layers in real time.
This paper combines ellipsometry with attenuated total reflection (ATR) for in situ studies at the solid/liquid interface. Angular spectra of reflected and transmitted light were calculated for a multilayer structure: an AMP 95 inhibitor layer (0.7 µm, n=1.47) and iron oxide on an iron substrate (complex n=2.86+3.86i). Probing used right circularly polarized light at λ=0.64 µm, incident through an ATR prism with ε=10.
Analysis of amplitude reflection coefficients R_p and R_s revealed anomalous behaviour of ellipsometric parameters ρ and Δ. In reflected light spectra, a sharp sign reversal of Δ near 20° was observed, indicating a transition from right circular to left elliptical polarization. In transmitted light spectra, sign inversion of Δ occurred both near 20° and over a wide range from 40° to 70°, which fundamentally differs from standard measurement conditions where Δ remains always positive.
The discovered polarisation effects and unique angular spectrum topology can be applied in experimental studies for non destructive testing, parameter verification, and efficiency assessment of anticorrosive inhibitor coatings. These findings provide a basis for improved optical monitoring of thin protective layers, enhancing sensitivity to structural changes and enabling more accurate evaluation of coating performance.

Speaker

Godlyauskas Oleg Vladislavas
Volgograd State University
Russian Federation

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