Abstract
Pd-Ni/TiO2 composite coatings were elaborated on 316L stainless steel by an electrodeposition method. The specimens were obtained from an electrolytic bath that contained various contents (5, 10, and 15 g L−1) of nanosized TiO2 particles. X-ray diffraction (XRD) characterization showed that increasing the TiO2 content in the coatings can decrease the crystal grain size. The surface morphology and chemical composition of the composite coatings were modified by the addition of TiO2 particles in the electrolyte, as shown by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) methods, respectively. The TiO2 content also significantly affected the mechanical and electrochemical properties of the Pd-Ni/TiO2 composite coatings. The microhardness of the Pd-Ni/TiO2 composite coatings can be enhanced by increasing the TiO2 content in the coatings. With the addition of 5 g L−1 TiO2 particles to the electrolyte, the deposited Pd-Ni/TiO2 composite coating presented a remarkably increased corrosion resistance when exposed to a sulfuric acid solution at 60 °C compared with that of the Pd-Ni alloy coating. Nevertheless, the further addition of TiO2 particles into the electrolytic bath did not further improve the corrosion resistance of the composite coating.
Highlights
Stainless steel is commonly used in various applications because of its favorable corrosion resistance
The Pd peaks are displayed at 40.1◦, 46.7◦, 68.1◦, and 86.6◦, whereas the Ni peaks are located at 44.5◦, 51.8◦, 76.4◦, and 92.9◦ [23], because metallic palladium and nickel are both face-centered cubic (FCC) crystalline phases according to Bragg’s equation
Pd-Ni/TiO2 composite coatings with approximately 1 μm thickness were obtained from an electrolytic bath that had various concentrations of TiO2 using an electrodeposition technique
Summary
Stainless steel is commonly used in various applications because of its favorable corrosion resistance. In some industries, such as the synthetic fiber industry, waste heat recovery, and alternative energies (i.e., proton exchange membrane (PEM) fuel cells and hydrogen production by water electrolysis), stainless steel is prone to corrosion in hot dilute sulfuric acid. Different techniques are used to elaborate coatings on stainless steel, such as chromium nitride coatings on stainless steel for conductive components using physical vapor deposition (PVD) [2] and superior tribological properties, corrosion resistance and biocompatibility of titanium-amorphous carbon-coated 316L stainless steel (SS) through magnetron. Coatings 2018, 8, 182 sputtering [3], etc These techniques cannot be applied to large-scale or special-shape workpieces, and several methods are not economical due to their intensive energy consumption.
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