Achieving synergistic wear and corrosion resistance in Ni-P coatings via ultrasonic power optimization: a microstructural and mechanistic study

To overcome the slow deposition, low density, weak adhesion and poor synergistic corrosion -wear resistance of electroless Ni-P coatings on 6061 Al alloy, ultrasonic-assisted plating was investigated. The effects of ultrasonic power on microstructure, mechanical properties, and corrosion behaviour were studied using SEM, EDS, XRD, electrochemical tests, and tribological experiments. At 180 W, ultrasonic treatment refined grains, increased coating density and crystallinity, and improved interfacial bonding. The friction coefficient decreased from 0.28 to 0.25, and the wear rate decreased from 1.73×10⁻⁶ to 8.67×10⁻⁷ g/(N·m). The corrosion current density dropped from 5.213×10⁻⁴ to 4.031×10⁻⁶ A·cm⁻², while the corrosion potential shifted from −0.487 to −0.462 V. These results demonstrate a synergistic enhancement of wear and corrosion resistance, providing a promising route for protective Ni-P coatings on 6061 Al alloy.