The Mechanism of Hydrogen Evolution at a Stainless Steel Electrode in Basic Solution

Abstract

The mechanism of the hydrogen evolution reaction at the stainless steel Type 304 (18.20% Cr, 18.20% Ni, austenitic) was investigated in the presence of plain NaOH solutions and with various ions added. It is concluded that the mechanism is (slow) HO+M+te = M-H; 2M-H > He Tafel parameters are given. While the hydrogen evolution reaction has been most frequently studied at the platinum (1), the dropping mercury (2), the iron (3-5), the silver (6,7), and the nickel (8-11) electrodes, it has yet to be studied at the commercial austenitic stainless steel (s.s.) Type 304 metal in strong sodium hydroxide solution. The electrolytic evolution of hydrogen at the s.s. 304 alloy in the alkaline media was undertaken because of the possibility of industrial application. The elemental composition of commercial austenitic s.s. 304 is listed as 18-20% Cr, 18-20% Ni, 2% Mn, 1% Si, 0.08% max C, 0.045% P, 0.03% S, and the rest Fe (12). The structure of the metal alloy is therefore very complex and, hence, its surface. Furthermore, a passivat-ing film of unknown structure and nature exists on the surface on exposure to air or oxidizing media (13).