The Role of Adsorbed CN Groups in the Hydrogen Embrittlement of Steel

Beck, W. Ken; Glass, A. L.; Taylor, Ellison H.

doi:10.1149/1.2423464

Cited by 26 publications

(12 citation statements)

References 7 publications

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“…[1][2][3] Inhibitors of both the HER and HAR are compounds which adsorb preferentially on the metal surface and hence decrease the hydrogen surface coverage, which in turn decreases the rate of both the HER and HAR. 1,2,7,33,34 By similar argument, others 8,9,11,35 attributed the effect of promoters of the HAR (Eq. 3) to inhibition of the recombination reaction (Eq.…”

mentioning

confidence: 74%

The Effect of Iodide Ions on the Kinetics of Hydrogen Absorption by Iron

Elhamid

Ateya

Pickering

2000

J. Electrochem. Soc.

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The presence of some additives in the environment affects the kinetics of the hydrogen evolution reaction (HER) on the surface (see Eq. 1 and 2) and, consequently, the hydrogen absorption reaction (HAR) within metals (Eq. 3). While some compounds inhibit both reactions, for example, benzonitrile, benzotriazole, and pyrroles, 1-7 others inhibit the HER while promoting the HAR, 8-28 e.g., iodide ions, thiourea, and aminotriazole. 1,2,8,15,[18][19][20][21] The mechanism of action of these additives is attracting considerable attention. [1][2][3] Inhibitors of both the HER and HAR are compounds which adsorb preferentially on the metal surface and hence decrease the hydrogen surface coverage, which in turn decreases the rate of both the HER and HAR. 1,2,7,33,34 By similar argument, others 8,9,11,35 attributed the effect of promoters of the HAR (Eq. 3) to inhibition of the recombination reaction (Eq. 2). This leads to a decrease in the rate of the HER (Eq. 2) but to an increase in the hydrogen surface coverage and hence to an increase in the hydrogen absorption. It has also been suggested that the adsorbed species, including iodide in acid sulfate solution, weaken the metal hydrogen bond 1,10,15,17 and hence facilitate the entry of hydrogen into the metal. Another group of authors attributed the accelerating affect of these additives on the HAR to an electronic interaction between the adsorbed hydrogen atoms and the adsorbed additive. 24,26,36 While additives with electron donating nature, such as iodide, 37 are reasoned to accelerate hydrogen absorption, those with electron withdrawing nature have the opposite effect. 24,26,36 Recently, Qian et al. 38,39 investigated the effect of arsenic oxide and hydrogen sulfide in promoting hydrogen absorption into iron and steel in alkaline solutions. Their results revealed that arsenic oxide enhances hydrogen absorption through its reduction to arsenic hydride (AsH 3 ). These authors concluded that AsH 3 is desorbed from the metal surface, thereby increasing the number of adsorption sites for hydrogen. Thus, the hydrogen surface coverage and, consequently, the hydrogen absorption rate are increased 38 as reported earlier. 8 In the case of hydrogen sulfide in alkaline solution, they concluded that HS Ϫ adsorbs on the surface, thereby, decreasing both the hydrogen surface coverage and the hydrogen desorption rate, although enhancing hydrogen absorption. 39 In a prior study of the Fe/H 2 S-acid system, Iyer et al. 40 concluded that H 2 S caused an increase in the hydrogen surface coverage and, in turn, accounted for the increase in the hydrogen absorption rate.The aim of the present study is to analyze the effects of iodide ions on the kinetics of both the HER and HAR on iron in a more in-depth manner than in the past. Of particular importance is the effect of iodide ions on the hydrogen coverage of the iron surface and the rate constant of the hydrogen absorption step which affects the rate of hydrogen permeation within iron. The analysis of the results makes use of models that ha...

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confidence: 74%

The Effect of Iodide Ions on the Kinetics of Hydrogen Absorption by Iron

Elhamid

Ateya

Pickering

2000

J. Electrochem. Soc.

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“…15 Beck et al have suggested that the poisons interfere with the H atom recombination step (reaction 3) in the cathodic evolution of H 2 . 23 According to this model the presence of the poison reduces the number of active sites for hydrogen adsorption on the Pd surface and, as a consequence, the rate of H 2 evolution is decreased. As a result the rate of formation of absorbed hydrogen from the adsorbed hydrogen intermediate,…”

Section: Resultsmentioning

confidence: 99%

The effect of surface species on the rate of H sorption into nanostructured Pd

Bartlett

Marwan

2004

Phys. Chem. Chem. Phys.

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Studies of the hydrogen region of nanostructured H 1 -e Pd films in 1 M sulfuric acid in the presence of crystal violet, or when small amounts of Pt are deposited on to the surface, show that the adsorption of hydrogen onto the metal surface is suppressed but that at the same time the kinetics of absorption of hydrogen into the Pd to form the b-hydride are significantly enhanced suggesting that the strongly adsorbed hydrogen on the Pd surface acts as a blocking layer for absorption of hydrogen into the Pd lattice.

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“…Many researchers have investigated hydrogen evolution and hydrogen absorption reaction kinetics using the results of Tafel slopes for i entry and i per . 9,26,27) When assuming the reaction rate of hydrogen absorption reaction (Eq. (4)) is much faster than that of the Volmer reaction (Eq.…”

Section: Current Responses To Cathodic Polarizationmentioning

confidence: 99%

“…Ammonium thiocyanate (NH 4 SCN) 8) is often added to aqueous solutions to enhance the hydrogen absorption of steels undergoing electrochemical hydrogen charging. Among other poisons, such as hydrogen cyanide (HCN), 9) sodium arsenate (NaAsO 2 ), 10) and hydrogen sulfide (H 2 S), 11) NH 4 SCN is the least toxic. However, the effects that different solution conditions, such as varying pH and NH 4 SCN concentration, have on hydrogen absorption have rarely been studied.…”

Section: Introductionmentioning

confidence: 99%

Effects of Ammonium Thiocyanate and pH of Aqueous Solutions on Hydrogen Absorption into Iron under Cathodic Polarization

et al. 2021

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To evaluate the susceptibility of steels to hydrogen embrittlement, it must be hydrogen charged and have its hydrogen content controlled before any mechanical testing. In this study, hydrogen permeation tests of an iron sheet were performed during potentiostatic hydrogen charging in various solutions containing ammonium thiocyanate to obtain a guideline for efficient hydrogen charging for a wide range of hydrogen contents. As the polarization potential shifted in the negative direction, the hydrogen permeation current increased before becoming almost constant. In all cases, besides when an aqueous sodium hydroxide solution was employed, the hydrogen permeation current increased due to the addition of ammonium thiocyanate. The effect of adding ammonium thiocyanate was enhanced as the aqueous solution pH was decreased. The hydrogen permeation current under various hydrogen charging conditions obtained in this study can be used as a reference for hydrogen charging of steels.

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The Role of Adsorbed CN Groups in the Hydrogen Embrittlement of Steel

Cited by 26 publications

References 7 publications

The Effect of Iodide Ions on the Kinetics of Hydrogen Absorption by Iron

The Effect of Iodide Ions on the Kinetics of Hydrogen Absorption by Iron

The effect of surface species on the rate of H sorption into nanostructured Pd

Effects of Ammonium Thiocyanate and pH of Aqueous Solutions on Hydrogen Absorption into Iron under Cathodic Polarization

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