Improving the tribological and corrosion behavior of NiB coating with low boron content from optimized lead-free bath on aluminum alloys

Abstract

This study focuses on producing environmentally friendly, lead-free nickel‑boron (NiB) coatings as an alternative to hard chromium coatings. Using the electroless method, the NiB coatings were fabricated from a lead-free bath, and the effects of varying B and Ni concentrations on the coatings' chemical composition, surface morphology, hardness, corrosion resistance, and wear performance were investigated. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to analyze surface morphology and phase composition. Corrosion performance was evaluated using potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS), while wear behavior was tested at sliding speeds of 20, 30, and 40 cm/s. The study highlights the critical role of sliding speed on wear mechanisms, friction coefficient, wear rate, and surface morphology. The analyses revealed that the optimal NiB coating, containing 34 g/L Ni and 3 g/L B, exhibited the highest hardness, the lowest corrosion rate, and the highest wear rate performance. The values obtained from these analyses were 891 HV for hardness, 8.87 × 10⁻⁶ mpy for corrosion rate, and 2.21 × 10⁻⁴ mm³/N·m for wear rate. The use of analysis of variance (ANOVA) identified key factors influencing these properties. The findings suggest that optimizing boron and nickel concentrations significantly enhances NiB coatings' corrosion resistance and wear performance, making them suitable for industrial applications.