Cu Plating with Sn and Subsequent Bronze Formation under Mild Conditions

Takahiro Suzuki,Masayuki Inoue

doi:10.1021/acs.jchemed.0c00552

Abstract

In a well-known bronze plating experiment, a Cu coupon is subjected to Sn plating and heating with a Bunsen burner. Currently, aqueous NaOH or HCl is typically used as the plating solution; however, the use of a strong acid or base provides operational risks, particularly in educational settings (e.g., schools). Herein, we introduce a modified method that uses aqueous NaHSO4 as the plating solution. This method reduces the operational risks and allows for the smooth deposition of silver-white Sn onto the Cu coupon in a higher yield than that obtained by the HCl method, which uses 30 times the concentration of the solute. When the Sn-plated Cu coupon is heated, it changes to bronze plating. This experiment is ideal for high school students, as it allows them to observe metal plating and solid diffusion.

Highlights

Plating and alloying are essential metalworking technologies and the subjects of many experimental reports.[1−3] In particular, “Copper into Gold: The Alchemist’s Dream” is a well-known experimental demonstration of brass plating using an NaOH solution (6 mol/L) and Zn powder.[4]
The “Copper to Silver to Gold” experiment reported by Shakhashiri in 1992 is an example of a bronze plating demonstration.[7]
When using the plating solution of this experiment, the potential upon contact between the Cu coupon and Sn is the electrochemical potential at which the underpotential deposi

Summary

■ INTRODUCTION

Plating and alloying are essential metalworking technologies and the subjects of many experimental reports.[1−3] In particular, “Copper into Gold: The Alchemist’s Dream” is a well-known experimental demonstration of brass plating using an NaOH solution (6 mol/L) and Zn powder.[4]. Because a high-concentration aqueous NaOH solution is heated close to its boiling point and handled in an open beaker, the experiment raises safety concerns (i.e., bumping, spilling of the solution, and producing a large amount of irritating fumes). To address this issue, our laboratory reported an effective method for plating Sn onto Cu by adding SnCl2, tin sand, and an anionic surfactant to HCl (3 mol/L). The tin-plated Cu coupon is heated with the oxidizing flame of a Bunsen burner for approximately 7 s followed by quenching with tap water

■ BACKGROUND

■ PROCEDURE

■ RESULTS AND DISCUSSION

■ ACKNOWLEDGMENTS

■ REFERENCES

■ CONCLUSIONS