Corrosion inhibition of copper by sodium phytate in NaOH solution: Cyclic voltabsorptometry for in situ monitoring of soluble corrosion products

The ability to in situ monitor the formation and transition of soluble corrosion products generated during metal electrochemical processes is important for elucidating the corrosion mechanism. The combination of cyclic voltammetry and cyclic voltabsorptometry allows simultaneous measurements of the potential-dependent current and absorbance, the latter of which corresponds to the characteristic wavelength of each light-absorbing species. For this purpose, a long-optical-path thin-layer electrochemical cell (LTE-cell) was fabricated to study the corrosion inhibition of copper by phytate in alkaline media. A conventional electrochemical cell was also used for common cyclic voltammetry and impedance spectroscopy. The morphology of the corroded copper surfaces was characterized using field-emission scanning electron microscopy. A high corrosion inhibition efficiency (ca. 90%) of phytate on copper was achieved in 0.1 mol dm−3 NaOH solution. Phytate was shown to promote the formation of the soluble intermediate cuprous ions and hinder the generation of the cupric ions from pitting corrosion of the initially deposited cuprous oxide layer. The integrity of the cuprous passive layer was therefore maintained, which strongly suppressed further formation of various cupric corrosion products. The results of this study indicate that cyclic voltabsorptometry based on a LTE-cell is an effective method for studying metal corrosion processes that involve light-absorbing ions.

► Derivative cyclic voltabsorptometry (DCVA) to monitor soluble corrosion products. ► DCVA reveals potential-dependent formation and chemical transition of soluble ions. ► IP6 greatly inhibits pitting corrosion of copper in NaOH. ► IP6 gives different effects on the intermediate cuprous and stable cupric ions.