Titrimetric determination of free boric acid and tetra- fluoroboric acid in nickel plating baths

Significance of the Topic

This approach enables direct quantification of two key additives in nickel plating baths—boric acid and tetrafluoroboric acid. Accurate control of their concentrations is vital for bath buffering, conductivity, deposit morphology, and overall process reproducibility.

Objectives and Study Overview

The bulletin presents a potentiometric titration protocol for simultaneous determination of free H3BO3 and HBF4 in nickel plating solutions. Complexation with mannitol allows distinct titration endpoints for each acid, enabling a single-step analytical procedure unaffected by nickel or co-present metal ions.

Methodology

Sample aliquots are diluted with water and 10% D-mannitol solution, which forms borate complexes. Titration with 0.1 M NaOH is conducted under magnetic stirring. Two equivalence points correspond to the stepwise liberation of fluoride and borate from their complexes.

Instrumentation Used

• Potentiometric titrators: 702 SET/MET, 716 DMS, 736 GP, 751 GPD, 785 DMP or 796 Titroprocessor
• 700 Dosino or 685 Dosimat dosing units
• Magnetic stirrer (2.728.0040)
• Exchange unit (6.3014.223)
• Combined LL pH glass electrode with cable (6.0222.100, 6.2104.020)

Main Results and Discussion

Typical titrations yield two well-defined endpoints. Example data: EP1 at 0.834 mL NaOH (HBF4 = 29.29 g/L), EP2 at 2.786 mL (H3BO3 = 48.28 g/L). The method displays high selectivity: nickel and alloying metals do not disturb the endpoint detection.

Benefits and Practical Applications

• Direct analysis in plating baths without prior separation
• Rapid, automated operation suitable for routine quality control
• High specificity due to mannitol complexation
• Quantitative determination of two acids in a single titration

Future Trends and Opportunities

Integration of inline titration modules for real-time process monitoring. Development of miniaturized sensors and automated dosing systems will enhance throughput. Application of advanced endpoint detection algorithms using machine learning could further improve precision and reduce analysis time.

Conclusion

The described titrimetric method offers a robust, efficient, and interference-free solution for simultaneous determination of boric and tetrafluoroboric acids in nickel plating baths, supporting optimized process control and product quality.

References

• Scholz E. Die Analyse von Fluoroboratbädern und anderen Fluoroboratlösungen. Galvanotechnik. 1975;66:811–819.
• Strohm D. Automation komplexer Titrationen am Beispiel eines galvanischen Nickelbades. GIT. 1988;32:369–373.