Effect of Ammonium Thiocyanate on Hydrogen Absorption by Cathodic Charging in Weak Alkaline Solution

T Kamisho and R Ishii and M Tsuda, ISIJ INTERNATIONAL, 64 (2024).

DOI: 10.2355/isijinternational.ISIJINT-2023-269

To clarify the mechanism underlying hydrogen absorption enhancement by adding ammonium thiocya-nate (NH4SCN) during cathodic charging in a weak alkaline solution, we constructed a kinetic model of the hydrogen evolution reaction and the hydrogen absorption reaction and performed analysis by fitting the kinetic model to the cathodic current density and steady-state permeation current density obtained from hydrogen permeation tests. Hydrogen permeation tests were conducted on pure iron by constant potential polarization at the hydrogen entry side in a weak alkaline solution with or without NH4SCN. The results indicated that NH4SCN enhances hydrogen absorption into pure iron as a result of the increasing surface hydrogen coverage on iron due to the suppression of the chemical hydrogen recombination reac-tion (Tafel reaction) and the electrochemical hydrogen desorption reaction (Heyrovsky reaction) in this condition.

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