engleski

An investigation of the surface damage of hot plates after black oxide coating

After the black-oxide coating brown stains were observed forming on the surfaces of grey-cast-iron hot plates made for an electric stove. These stains were metallographically examined using a scanning electron microscope (SEM) equipped with an energy-dispersive X-ray spectrometer (EDXS). For the phase identification we also employed X-ray diffraction (XRD) analyses. The results of the analyses indicated that the stained surfaces of the hot plates were covered with whiskers of hematite (Fe2O3), while on the surfaces of the non-defective hot plates only magnetite (Fe3O4) was present. The thermodynamic calculations confirmed the possibility of the formation of hematite (Fe2O3) as a result of the oxidation of magnetite (Fe3O4) if the partial pressure of oxygen is increased during the black-oxide-coating process.

whiskers; grey cast iron; magnetite (Fe3O4); hematite (Fe2O3)

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