The adsorption and diffusion of electrolytic hydrogen in palladium

Abstract

A sensitive electrochemical technique, which permits the recording of the instantaneous rate of permeation of electrolytic hydrogen through palladium, is described. Results were obtained under conditions required by theory for the diffusion of hydrogen with the use of electronic potentiostats. Analysis of the results shows the validity of the equations previously deduced for the diffusion of hydrogen. No anomalies in the diffusion have been found under these conditions. Thus the diffusion constant is found to be independent of thickness in the range 0·0035 to 0·054 cm. The permeation has been found to be inversely proportional to thickness as required by theory. The diffusion constant for a hydrogen poor α-palladium has been found to be 1·30 ± 0·20 x 10 -7 cm 2 s -1 at room temperature. Reasons for permeation anomalies reported in the literature for diffusion of hydrogen from the gas phase are discussed. Attention is drawn to errors in the classical time lag determination which unless corrected, can give rise to spurious thickness and temperature dependence of the diffusion constant.

Inhibition effect of underpotential deposition of metallic cations on aqueous corrosion of metals

“…Rashkov et al (1988) investigated the relation between Zn-UPD and penetration of hydrogen in Armco iron. The Devanathan-Stachurski method (Devanathan & Stachurski, 1962, 1964 was used for the measurement of hydrogen penetration rate through a bipolar iron membrane. The electrolytes employed in the cathodic compartment for hydrogen evolution were deaerated 1 m Na 2 SO 4 + 0.2 m NaCl + 0.5 m H 3 BO 3 solutions without and with 10 −3 m-1 m ZnSO 4 .…”

“…The presence of Zn 2+ also decreased the oxidation current of the atomic hydrogen in the anodic compartment, indicating that the Zn-UPD on Armco iron inhibits both the hydrogen evolution and the penetration of atomic hydrogen. Popov et al (1994a) also investigated the effect of Zn-UPD on hydrogen absorption and penetration into HY-130 steel by using the Devanathan-Stachurski method (Devanathan & Stachurski, 1962, 1964. The electrolytes employed in the cathodic compartment for hydrogen evolution were deaerated 1 m Na 2 SO 4 + 0.4 m NaCl + 0.4 m H 3 BO 3 solutions without and with 2 × 10 −3 m ZnSO 4 .…”

“…However, the inhibition effect of Zn 2+ was observed up to potentials more positive than the potential region of Zn-UPD, which was ascribed to the shift in anodic stripping potential of Zn toward the positive direction due to irreversible electro-deposition of Zn or due to alloy formation of Zn with substrate steel. Zheng et al (1993) investigated the effect of Pb 2+ on hydrogen evolution and permeation into AISI 4340 steel in deaerated 0.5 m HClO 4 + 0.25 m NaClO 4 solution by using the Devanathan-Stachurski method (Devanathan & Stachurski, 1962, 1964. Two characteristic cathodic current peaks at −0.15 V and −0.24 V which correspond to the UPD and bulk deposition of Pb, respectively, appeared during cyclic voltammetry of AISI 4340 steel in solution with 2 × 10 −3 m Pb 2+ .…”

Hydrogen Diffusivity and Trapping in Custom 465 Stainless Steel

“…The heating and cooling rates were 10 • C/min and 40-60 • C/min, respectively. After aging, all specimens were ground on both sides on a 1000 grit SiC grinding paper and polished with 6 μm and 1 μm diamond pastes.Electrochemical hydrogen permeation (EP).-The EP tests were carried out in a two-compartment cell, originally developed by Devanathan and Stachurski,[10][11][12] with the 0.12-0.2 mm thick specimen being a membrane separating between the two compartments, as described in Ref. 4.…”

Numerical Study of Hydrogen Trapping: Application to an API 5L X60 Steel

“…Gas phase charging ensures a constant and reliable chemical potential of hydrogen at the input surface [12]. The electrochemical detection technique is according to Devanathan and Stachurski [13] in an experimental arrangement similar to that outlined in [14]. This arrangement consists of two compartments (input cell and detection cell) separated by the steel permeation membrane which has an exposed area of 1.9 cm 2 on both their entry and exit surfaces.…”