Characterization of Electroless Nickel–Boron Deposit from Optimized Stabilizer-Free Bath

• Main Authors: Muslum Yunacti, Alexandre Mégret, Mariana Henriette Staia, Alex Montagne, Véronique Vitry
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: Coatings
• Subjects: electroless nickel–boron deposit; environmentally friendly deposition; stabilizer; reducing agent; plating rate; characterization
• Online Access: https://www.mdpi.com/2079-6412/11/5/576

Conventional electroless nickel–boron deposits are produced using solutions that contain lead or thallium, which must be eliminated due to their toxicity. In this research, electroless nickel–boron deposits were produced in a stabilizer-free bath that does not include any toxic heavy metal. During processing, the plating rate increased from 10 to 14.5 µm/h by decreasing the concentration of the reducing agent, leading to increased bath stability. The thickness, composition, roughness, morphology, hardness, wear, and corrosion resistance of the deposits were characterized. The new deposit presents an excellent hardness of 933 ± 56 hv₅₀, 866 ± 30 hk₅₀, and 12 GPa from the instrumented indentation test (IIT), respectively, which are similar to that of hexavalent hard chromium coating. Moreover, by using both potentiodynamic polarization and salt spray tests it was shown that the coating presents higher corrosion resistance as compared to standard nickel-boron coatings. The new deposit exhibits properties close to those of the conventional electroless nickel–boron deposits. Therefore, it could replace them in any industrial applications.