Diffuse reflection spectroscopy as a tool to measure low surface coverage of metal substrates by metallic oxide particles

Deposition of particles from a circulating fluid is a common industrial problem causing fouling or radioactive contamination in circuits of nuclear power plants. A few experimental methods have been developed to study the adhesion process of particles in order to determine the deposition kinetics. This work describes a setup based on diffusion reflectometry of visible light to perform real-time in-situ measurements. The deposition of magnetite and hematite particles onto stainless steel was studied by recording spectra of reflected visible light for several surface-coverage values. Scanning electron microscopy has shown that magnetite particles do not form a uniform layer. Simulations of the evolution of the reflected intensity as a function of the deposited amount of both oxides were performed on the basis of their absorption coefficients and particle sizes. The agreement between theoretical and experimental results shows that diffuse reflection spectroscopy could be a helpful in-situ method of quantifying fouling kinetics of metallic surfaces.