With the international drive to deploy green energies and decarbonized intermediates in the place of fossil fuel sources, a large number of developed countries are actively preparing for a future where hydrogen plays a strategic role as an energy storage medium. Producing and using hydrogen requires the rapid expansion of a dedicated, economically viable industrial sector. Nevertheless, questions on how to safely store, transport and distribute hydrogen remain an important priority today. In countries with existing natural gas transport grids, the possibility to retrofit these networks to store and transport hydrogen-natural gas blends is being studied. A key challenge is to evaluate how pressurized H2 would interact with steel structures with regards structural embrittlement of the latter, with a view to exploiting existing transport infrastructures for storage and transport applications. In this work, we evaluate the H2-performance of a non-hydrogen service ×65 pipeline steel. The cracking susceptibility of this steel grade has been evaluated at 100 bar H2 using slow strain rate testing, Constant strain testing and fracture toughness measurements. Accompanying hydrogen permeation tests under pressure provide diffusion data and elucidate the discussion. Exposures were carried out in dry or wet H2 and with or without H2S contamination at levels representative of biogas. The results underline that the impact of dry or wet hydrogen on this grade are moderate. The presence of traces of H2S together with humidity could risk seriously degrading the mechanical performance of the ×65 steel grade. © 2023 The Authors

The presence of dissolved hydrogen sulfide in upstream or refining fluids is known to encourage hydrogen-induced mechanical failures of carbon or low alloy steel. Historically, the solution pH and the gaseous partial pressure of H2S (PH2S, bar) are used to evaluate an aqueous environment’s severity during materials corrosion cracking qualification. However, in recent years, it is suggested that the H2S fugacity (fH2S, an effective H2S partial pressure in bar) and actual dissolved H2S concentration ([H2S]aq) be used, rather than the PH2S, to better account for the effect of total pressure on steel corrosion cracking performance. In this paper, results obtained in a Joint Industry Programme (JIP) focused on evaluating the effect of fH2S on the hydrogen permeation across upstream steels using hydrogen pressure probe sensors and electrochemical Devanathan-Stachurski permeation tests are presented. A positive correlation between H-permeation rate at steady-state and environment fH2S or [H2Saq] is measured for numerous carbon steel grades in acetate-buffered 5% NaCl solution at pH 4 and PH2S ( 1bar), tested at total pressure between 1 – 300 bar. Furthermore, hydrogen induced cracking of a susceptible carbon steel grade increases when evaluated as a function of increasing fH2S for the same PH2S/pH combination.

The presence of dissolved hydrogen sulfide in upstream or refining fluids is known to encourage hydrogen-induced mechanical failures of carbon or low alloy steel. Historically, the solution pH and the gaseous partial pressure of H2S (PH2S, bar) are used to evaluate an aqueous environment’s severity during materials corrosion cracking qualification. However, in recent years, it is suggested that the H2S fugacity (fH2S, an effective H2S partial pressure in bar) and actual dissolved H2S concentration ([H2S]aq) be used, rather than the PH2S, to better account for the effect of total pressure on steel corrosion cracking performance. In this paper, results obtained in a Joint Industry Programme (JIP) focused on evaluating the effect of fH2S on the hydrogen permeation across upstream steels using hydrogen pressure probe sensors and electrochemical Devanathan-Stachurski permeation tests are presented. A positive correlation between H-permeation rate at steady-state and environment fH2S or [H2Saq] is measured for numerous carbon steel grades in acetate-buffered 5% NaCl solution at pH 4 and PH2S ( 1bar), tested at total pressure between 1 – 300 bar. Furthermore, hydrogen induced cracking of a susceptible carbon steel grade increases when evaluated as a function of increasing fH2S for the same PH2S/pH combination.

The highly corrosive behavior of ammonium chloride (NH4Cl) is known to originate from its intrinsic hygroscopic nature. Refining and co-processing process units for biofuels are often exposed to highly concentrated NH4Cl solution either resulting from water vaporization from an HCl and NH3 containing solution when the temperature increases or salt deposition from vapor phase when the temperature drops. For the latter case, once it reacts with water vapor present in the process, the deposited NH4Cl salts forms a concentrated and corrosive solution through deliquescence (unlike in conventional refinery). Consequently, severe pitting and localized corrosion are reported in hydrogenation and fluid cracking units. Therefore, studying corrosion resistance alloys (CRA) compatibility in the presence of concentrated NH4Cl salt solution is crucial to mitigate corrosion in the process. This paper reports the experimental evaluation of corrosion resistance of different CRAs, based on corrosion rate and stress corrosion cracking, exposed to saturated NH4Cl solution in the temperature range of 130-220°C. 

The highly corrosive behavior of ammonium chloride (NH4Cl) is known to originate from its intrinsic hygroscopic nature. Refining and co-processing process units for biofuels are often exposed to highly concentrated NH4Cl solution either resulting from water vaporization from an HCl and NH3 containing solution when the temperature increases or salt deposition from vapor phase when the temperature drops. For the latter case, once it reacts with water vapor present in the process, the deposited NH4Cl salts forms a concentrated and corrosive solution through deliquescence (unlike in conventional refinery). Consequently, severe pitting and localized corrosion are reported in hydrogenation and fluid cracking units. Therefore, studying corrosion resistance alloys (CRA) compatibility in the presence of concentrated NH4Cl salt solution is crucial to mitigate corrosion in the process. This paper reports the experimental evaluation of corrosion resistance of different CRAs, based on corrosion rate and stress corrosion cracking, exposed to saturated NH4Cl solution in the temperature range of 130-220°C. 

This paper presents the results of a study aiming at evaluating the effect of austenite spacing on the sour cracking resistance of a duplex stainless steel. The stress corrosion cracking resistance was assessed using slow strain rate (SSRT) and constant load tests. Under SSRT, a clear effect of the austenite spacing is observed. Above a threshold spacing, the pH-pH2S acceptability domains are smaller as the austenite spacing increases. This effect is however not seen under constant load at 90% of the actual yield strength, suggesting that a dynamic straining or a large plastic strain is needed to highlight the effect of this parameter.

To evaluate the possibility of hydrogen storage in depleted gas reservoirs, natural gas storage facilities, aquifers and salt caverns, the applicability of ferritic pearlitic K55 and tempered martensitic L80, both very frequently used as casings and tubings, has been investigated. Materials were investigated by means of high-pressure, high-temperature autoclave tests and analyses of the hydrogen uptake. The autoclave tests were performed on tensile specimens loaded with a spring at 90 % of the specified minimum yield strength, additionally the samples were analysed to determine the hydrogen uptake. Different gas compositions were considered (pure hydrogen, with or without the presence of CO2/H2S) under a hydrogen partial pressure of 120 bar. The tests were conducted in dry or wet environments. From the results, it can be seen that the hydrogen uptake is low even under the most severe conditions. However, from the mechanical test conducted in this study, it appears that the ferritic pearlitic K55 steel seems to be a suitable pipe material for underground hydrogen storage, and the higher strength steel L80 steel can be used only in non-sour environments (no significant amount of H2S in the reservoir, which is a priori the case of underground storages). 

In France, deep geological disposal is considered for the storage of high and intermediate-level long-lived radioactive wastes. For aluminium, the possibility to encapsulate the wastes in a cement-based matrix is studied. However, cement being an alkaline environment, aluminium can lose its passivity, starts to corrode leading to hydrogen evolution in the infrastructures and generate a possible explosive hazard after decades of storage if hydrogen can accumulate somewhere in the facility. It is therefore necessary to study the corrosion behaviour of aluminium in the different cements considered for the encapsulation to estimate the possible amount of hydrogen that could be generated through corrosion and design the cement capsules accordingly. This work mainly focused on the reaction occurring at the aluminium-cement interface. Raman spectroscopy did not highlight significant differences in the nature of the corrosion products forming at the cement/aluminium interface, leading to the conclusion that it is not the chemistry of the cement that is the key factor controlling the corrosion rate but rather the physical properties of the cement matrix. 

In this study, the effect of test conditions on the formation of selective dissolution during sour testing was investigated on a cold-rolled duplex stainless steel UNS S32750. All experiments were conducted in NaCl 150 g/L and pH2S = 0.3 bar. Different pHs between 3.3 and 4.5 were studied at 80°C. Based on tests performed under varying conditions, it is demonstrated that selective dissolution (SD) competes with cracking and that under conditions leading to the formation of a large area with SD, the presence of this type of corrosion can hide the susceptibility of the material to cracking. The presence of only SD after testing must therefore be considered with caution. SD initiated also without applied stress showing that the phenomenon is correlated to a loss of passivity. From electron backscattered diffraction (EBSD) analyses and electrochemical monitoring the formation of SD under the test conditions considered in this work is correlated to the instability of the passive film and not to any superficial singularities of the material or specific crystallographic orientations. 

Depending on the lifetime and level of radioactivity of radioactive wastes, different disposal facilities are considered. Though low- and intermediate-level short-lived waste can be disposed in surface disposal facilities, deep geological disposal is considered for high- and intermediate-level long-lived waste. In France and Belgium, long-term disposal is studied in clay host rock media. For aluminum, the disposal concept is based on encapsulation of the waste in a cement-based matrix. It is also well-known that aluminum is prone to severe corrosion in sufficiently alkaline environments leading to possible hydrogen production. To ensure the safety of the disposal facilities and the integrity of the cement capsules, the amount of aluminum that is disposed in each waste package must be specified and is limited to mitigate the level of hydrogen production by aluminum corrosion. In the present study, the corrosion resistance of an aluminum alloy (grade EN-AW-5754/H111) in two different cement matrices was studied in different configurations at room temperature. In each case, the evolution of hydrogen production was monitored to address the corrosion rate variation versus time.