Investigation of Black Chromium Coatings Modified with Silicon Oxides on AISI 304 Steel

Abstract This study aimed to investigate the effect of silicon oxide additive on the structure of black chromium coatings produced by electrochemical deposition. The scanning electron microscopy and energy-dispersive X-ray spectroscopy methods were used to study the morphology and elemental composition of chromium oxide coatings formed on AISI 304 stainless steel. The electrochemical impedance spectroscopy (EIS) method was used to study the electrochemical properties of the coating as well as to assess its subsurface structure. It was found that adding silicon oxide to the electrolyte enables the formation of a crack-free coating, while variations in its concentration influence the crystallite size of the deposited structure. An increase in the concentration of silicon oxides in the electrolyte results in a higher silicon content in the coating. The EIS results show that the increasing resistance of the coatings formed in modified electrolytes indicates an improvement of their protective properties. An analysis of equivalent circuits allows to make conclusions on the layered structure of the obtained coatings.