Composite plating improves functionalities of wear resistance, corrosion resistance, lubricity, etc. through co-deposition with suitable particles. For this study, reactive metallic particles were introduced intentionally as a dispersant. Heat treatment was used to form an alloy with a plated matrix. Composite plating films were formed using electroless Ni-P plating with Nb powder of two types as dispersants: nanopowder (ca. 300 nm diameter) and micropowder (ca. 50 μm diameter). The composite plating film was alloyed using heat treatment at 800°C for 1 hour under vacuum conditions. X-ray diffraction (XRD) analysis confirmed that the proportion of alloy to reactive composite film with nanopowder was much larger than that with micropowder. Results of X-ray photoelectron spectroscopy (XPS) analyses suggest that a selective Nb oxide was formed on the composite film surface when using Nb nanopowder. On the other hand, almost no Nb micropowder was changed to alloy or oxide in the composite films. Using nanopowder, much of the composite plating film formed reactive composite plating film alloy during heat treatment.
To develop a highly corrosion-resistant anode electrode for use in alkaline water electrolysis, we evaluated three plated electrode samples: nickel-plated (Ni, used generally for water electrolysis), Ni-P1 (9.64 wt%P content nickel), and Ni-P2 (17.50 wt%P content nickel). The Ni-P alloy was expected to show high corrosion-resistance because Ni-P alloy containing over 8 wt%P has an amorphous structure. We compared their surface structures using XRD, compared their morphologies using SEM, and investigated their growth in situ using a quartz crystal microbalance (QCM). We also characterized their electrochemistry using CV. Because its smooth surface and distinct amorphous structure protect it against corrosion by the oxide film, Ni-P2 exhibited excellent resistance. Grain boundaries on the Ni surface caused partial corrosion, although the Ni surface was covered with a great amount of oxide film. Furthermore, Ni-P1 tends to corrode easily because it is considered to be in a transition state to an amorphous structure and has few grain boundaries on its surface. All samples exhibited almost identical oxygen overvoltage. Results show that Ni-P alloy (high P content), which had a fine amorphous structure and showed high corrosion-resistance, is a suitable anode electrode material for use in alkaline water electrolysis.