New electrical method for obtaining graphic information on the evaluation of the uniformity of ZrO2-3 mol% and Y2O3 coatings deposited by electrophoresis. Application in protection and finishing of dental parts

In recent years, the use of ceramic coatings has increased in industrial applications, using techniques such as immersion and electrophoretic deposition (EPD). High conductivity electrodes and metallic substrates, such as austenitic stainless steels, are crucial for uniform deposition, especially in the chemical and biomedical industries. ZrO₂-3mol% Y2O3 ceramic solutions serve as precursors in the fabrication of functional materials such as solid oxide fuel cells and biomedical applications. This work presents a novel electrical method to evaluate the homogeneity and uniformity of ceramic coatings on metallic specimens. The method is based on the application of an alternating current in a frequency range between 10 Hz and 10 MHz, measuring the impedance at 16 equidistant points. The impedance is decomposed into its real and imaginary components, and a map of the coating surface is generated, which allows the uniformity of the coating to be accurately assessed. To evaluate the results, the ZrO2-3mol% Y2O3 solution, the AISI 310 stainless steel metal substrate and the substrates coated (at different concentrations, for different times and current densities) and sintered at different temperatures were characterised. It was observed that the ZrO₂-3mol% Y₂O₃ solution at the following conditions (42.9 g-L^-1, 20 min, 1.5 A-cm^-2, 500 °C) presented the highest uniformity and homogeneity. In view of all the results, the proposed electrical method confirmed the uniformity and homogeneity of the coated surface from the capacitance values and their representation on a surface map. It is presented as a simple, inexpensive and non-destructive technique that provides information on the accuracy and sensitivity of the coating thickness and opens up its application to different industrial sectors. It also has great potential to revolutionise the field of medicine, offering more durable, biocompatible and efficient implantable devices.

Graphical Abstract