Accelerated Evolution of Hydrogen on Freshly Generated Metal Surfaces in Aqueous Solution

Abstract

Data have been obtained which describe quantitatively the rate of evolution of hydrogen on freshly generated surfaces of Fe, Cr, and their binary alloys. At low electrode potentials, creation of the new metal surface causes large acceleration of the rate of hydrogen evolution. The succeeding decay of cathodic current with time is relatively small; long after its creation, the new surface remains catalytically active towards hydrogen evolution provided the potential remains low. The kinetics of each stage of the process are defined and presented as a function of the metal composition.The scratched rotating disk electrode has proved a valuable probe for the investigation of the rapid initial reactions which occur when metal surfaces are generated in aqueous electrolytes under potential control (1-7). Efforts have so far been focused on the elucidation of anodic processes occurring in a range of metal/ electrolyte systems. These have included measurements of the rapid initial rates of anodic reactions (1-9), kinetics of oxide film growth (8,9), and the effects of anions on these (1, 2). Although cathodic current transients have been documented at sufficiently low potentials (2-9), these have not been analyzed in detail.Preliminary work on the scratched chromium electrode at low electrode potential in alkaline solution has shown that the hydrogen evolution reaction can be accelerated on scratching, and that the accelerated rate of reaction can continue for periods long after the scratching process is complete (10). The present work sets out the results of similar studies of iron, chromium, and a range of their binary alloys in a potential range where scratching gives rise to a net cathodic current due to the hydrogen evolution reaction occurring upon the scratch surface.The phenomenon of enhanced or retarded diffusivity of hydrogen atoms through metals accompanying plastic deformation has been studied for some time (11). Despite the recent debate (12-14) concerning the measurements and mechanism of this process, enhanced diffusion of hydrogen in metals undergoing plastic deformation may well be involved in the mechanisms of some localized environment-dependent failure modes, such as corrosion fatigue and hydrogen embrittlement (15-17). For the scratched electrode, enhanced rates of hydrogen evolution are possible (10), and there thus exists the likelihood of a combination of enhanced hydrogen discharge and subsequent rapid transport through the metal substrate. Such processes may be envisaged as having repercussions for environment-sensitive failure of metals. ExperimentalFull details of the potentiostatically controlled scratched electrode technique have been presented previously (1-7). The technique is designed for measurement of both the instantaneous and subsequent events that occur when a fresh metal surface is created in solutions under electrochemical control. The disk electrodes used in this work were made from Cr, Fe, and a range of iron/chromium binary alloys of compositions 5%, 20%, and 50% Cr. These are d...

Effect of Tensile Stress on the Passivity Breakdown and Repassivation of AISI 304 Stainless Steel: A Scanning Kelvin Probe and Scanning Electrochemical Microscopy Study

“…These findings are in agreement with the study of G.T. Burstein [39], which determined that newly formed surfaces accelerate the water reduction and hydrogen evolution reactions. The subsequent decay of the cathodic current over time is relatively small, and the new surfaces remain catalytically active towards hydrogen evolution [39].…”

“…Burstein [39], which determined that newly formed surfaces accelerate the water reduction and hydrogen evolution reactions. The subsequent decay of the cathodic current over time is relatively small, and the new surfaces remain catalytically active towards hydrogen evolution [39]. The SKP measurements in air correspond to the OCP measurements in a passivating aqueous electrolyte using a reversible reference electrode ( Figure 11).…”

Prove of hydrogen formation through direct potential measurements in the rolling slit during cold rolling

“…These processes are inevitable during the cold rolling. As shown by Anderson et al [26] and Burstein and Kearns [27] they are always accompanied by the formation of hydrogen on the freshly exposed metallic surface in the presence of aqueous media containing hydrogen ions.…”

“…Dedy et al [25] [26] studied the behaviour of surface potentials of different metallic electrodes, scraped inside the solutions with different pH and described the phenomenon of an accelerated hydrogen evolution on freshly cleaved metallic surfaces in aqueous medium; it has been widely reported since then in the literature. For example, Burstein and Kearns [27] did an excellent study on describing an accelerated evolution of hydrogen from freshly generated surfaces of Cr, Fe and their alloys.…”

Scanning Kelvin Probe Investigation of High-Strength Steel Surface after Impact of Hydrogen and Tensile Strain

“…However, the deformed area, even after 24 h of exposure in air, exhibited a potential that was 80-90 mV lower than the potential of the non-altered surface ( Figure 3C). The electrochemistry of freshly created surfaces developed Burstein and Kearns [37] showed accelerated hydrogen-reduction kinetics relative to the oxide-covered areas of the steel surface. Even without external load, the residual stress in the bulk might also influence hydrogen uptake in the steel as discussed by Lufrano and Sofronis [38].…”