1c184-h2 permeation

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Item No. 24002 NACE International Publication 1C184 (2008 Edition)

This Technical Committee Report has been prepared by NACE International Task Group 137* on Hydrogen Permeation Measurement and Monitoring

Hydrogen Permeation Measurement and Monitoring Technology

© June 2008, NACE International

This NACE International (NACE) technical committee report represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respect preclude anyone from manufacturing, marketing, purchasing, or using products, processes, or procedures not included in this report. Nothing contained in this NACE report is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent. This report should in no way be interpreted as a restriction on the use of better procedures or materials not discussed herein. Neither is this report intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefulness of this report in specific instances. NACE assumes no responsibility for the interpretation or use of this report by other parties. Users of this NACE report are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and for determining their applicability in relation to this report prior to its use. This NACE report may not necessarily address all potential health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this report. Users of this NACE report are also responsible for establishing appropriate health, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of this report. CAUTIONARY NOTICE: The user is cautioned to obtain the latest edition of this report. NACE reports are subject to periodic review, and may be revised or withdrawn at any time without prior notice. NACE reports are automatically withdrawn if more than 10 years old. Purchasers of NACE reports may receive current information on all NACE International publications by contacting the NACE FirstService Department, 1440 South Creek Drive, Houston, Texas 77084-4906 (telephone +1 281-228-6200).

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Foreword
This NACE technical committee report has been prepared to provide basic information on hydrogen permeation measurement and monitoring technology. It describes the background of hydrogen permeation measurement and monitoring technology, types of hydrogen monitors available, and some applications. This report is intended for use by professionals in the oil and gas industry (including production, transportation, and refining) concerned with equipment service in which hydrogen enters metals and alloys, usually steels. Applications fall into two categories: hydrogen entry in aqueous corrosive environments containing hydrogen
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promoters, and hydrogen entry associated with more diverse sources of hydrogen at higher temperatures (>100 °C [212 °F]). When steel corrodes in acidic media, atomic hydrogen is typically produced as a product of the cathodic corrosion reaction. A portion of the atomic hydrogen penetrates the steel and the balance combines to form molecular hydrogen (H2) and is released as bubbles of gas. The presence of promoters such as fluoride, sulfide, arsenic, or selenic compounds sometimes causes a significant portion of the hydrogen atoms to diffuse into steel. Hydrogen uptake of metals is not limited to acidic systems below pH 7. It can also occur at higher pH values when hydrogen is produced

___________________________ * Chair Dharma Abayarathna, Williams Gas Pipeline, Houston, TX.

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cathodically from hydrogen-containing oxidants, such as when bisulfide (HS–1) is reduced to sulfide (S–2), or by improperly operated cathodic protection systems. At higher temperatures, increased permeability of hydrogen in metals frequently causes appreciable hydrogen entry consequent to any reaction that liberates hydrogen at the metal surface, including the dissolution of H2 gas itself. An increase in temperature often also releases trapped hydrogen within a metal, which then migrates to the metal surface and is released as a hydrogen flux. Field applications for measurement of hydrogen flux from aqueous corrosion primarily involve sulfur compounds, especially hydrogen sulfide (H2S), which often occur in produced crude oil and gas streams. H2S may also be present in process stream condensates downstream from crude oil and gas production (e.g., in gas plants and sulfur-removal units). Additional H2S is released from the breakdown of sulfur compounds during certain refinery processes (e.g., in desulfurization processes such as hydrotreating and hydrocracking). Additionally, hydrogen flux is used to monitor hydrofluoric acid (HF) corrosion in HF alkylation units where the HF is a catalyst.

High-temperature field applications for hydrogen flux measurement include naphthenic acid and sulfidic corrosion, which accompany distillation of acidic and high-sulfur oil feedstock. Hydrogen also enters into metals and alloys at high temperatures in hydrogen-containing atmospheres or during manufacturing or fabrication operations. Measurement of hydrogen during bake-out operations following such processes is also of interest. Applications also exist in other industries, such as the chemical industry and plating industry (e.g., hot-dip galvanizing, electrochemical, and electroless metal plating).

Hydrogen monitors are used for various purposes depending on the design of the monitor. Each type of monitor is suited to one or more purpose. These include:

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(a) Quantifying the amount of atomic hydrogen formed by a corrosive environment, providing an indirect measurement of corrosion rate (all types of monitors); (b) Quantifying the amount of atomic hydrogen transmitted through a pipe or vessel wall because of a corrosion reaction at the entry face, providing a direct measurement of hydrogen flux available for damage mechanisms such as hydrogen-induced cracking (HIC) (external, nonintrusive monitors); (c) Quantifying the amount of hydrogen out-gassed from a metal or alloy during thermal treatments to remove hydrogen prior to operations such as welding (hydrogen collection method); and (d) Evaluating the effects of corrosion inhibitors (all types of monitors). This technical committee report was originally prepared in 1984 by NACE Task Group T-1C-9, a component of former Unit Committee T-1C—Corrosion Monitoring in Petroleum Production. Unit Committees T-1C and T-1D were combined, and this report was reviewed and reaffirmed in 1995 by Unit Committee T-1D—Corrosion Monitoring and Control of Corrosion Environments in Petroleum Production Operations. This report was revised in 2008 by Task Group (TG) 137—Hydrogen Permeation Measurement and Monitoring. TG 137 is administered by Specific Technology Group (STG) 62—Corrosion Monitoring and Measurement: Science and Engineering Applications and is sponsored by STG 31―Oil and Gas Production: Corrosion and Scale Inhibition and STG 34—Petroleum Refining and Gas Processing. It is issued by NACE International under the auspices of STG 62.

NACE technical committee reports are intended to convey technical information or state-of-the-art knowledge regarding corrosion. In many cases, they discuss specific applications of corrosion mitigation technology, whether considered successful or not. Statements used to convey this information are factual and are provided to the reader as input and guidance for consideration when applying this technology in the future. However, these statements are not intended to be requirements or recommendations for general application of this technology, and must not be construed as such.


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Hydrogen Monitors
Hydrogen monitors are sometimes divided into three basic types based on the hydrogen measurement transducer: (1) pressure or vacuum type, (2) electrochemical type, and (3) hydrogen collection type. Type (1) monitors register the increase in pressure or the loss of vacuum as a result of accumulation of H2 gas in a sealed volume. Type (2) monitors measure the amount of hydrogen that permeates through a metal surface by measuring the electrical current typically used to oxidize atomic hydrogen in an electrochemical cell. Type (3) monitors collect hydrogen in an air stream, which is then remotely detected. A variety of hydrogen probes using these monitors are currently available for both laboratory and field use. Descriptions of specific probes are provided in the following sections.
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Type (1)—Pressure Hydrogen Probes Pressure hydrogen probes are available in both intrusive and nonintrusive types (see Figures 1 and 2). Pressure hydrogen probes are generally accurate and easy to use. The accuracy depends on the precision of the pressure measurement. The main disadvantage to using pressure hydrogen probes is related to the increasing hydrogen pressure. Periodic bleeding is often conducted when using pressure hydrogen probes.

Figure 1

Schematic of an intrusive, type (1) pressure hydrogen probe.

Coated area

Internal volume

Exposure area

Cross-sectional view


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Figure 2

Schematic of a nonintrusive, type (1) pressure hydrogen probe.

Pressure gauge

Pipe or vessel wall

Bleed valve

The intrusive-type probes assess the corrosiveness of the test environment and respond quickly to changes in the environment because the tube wall is usually much thinner than the pipe or vessel wall. The tube walls are available in common carbon steel types that are in general use. They are usually made from steel similar to the pipe or vessel wall; however, they do not provide accurate information regarding the concentration of atomic hydrogen in the pipe or vessel wall itself, and therefore do not provide accurate information regarding susceptibility to hydrogen damage. Intrusive probes, also known as finger probes, consist of a steel tube sealed on one end and a bleed valve on the other end, creating an inner cavity with a known volume (see Figure 1). A pressure gauge attached to the valve end shows the measurement of the increase in pressure within the inner cavity as a result of accumulation of H2 gas. The outer surface of the steel tube is partially coated with polytetrafluoroethylene to provide a fixed surface area of exposure to a test environment. After probes are installed in the system, the fixed exposure area corrodes, generating atomic hydrogen. A portion of atomic hydrogen generated diffuses through the tube wall into the fixed probe volume and forms H2 gas through recombination on the hydrogen effusion side. The formation of H2 gas inside the probe cavity generates an increase in the gauge pressure. The use of intrusive probes of any type is limited by the availability of suitable access fittings or flanges to install the probes. Further, intrusive probes are typically only installed at fixed points and in fixed orientations and cannot be

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moved. If a suitably sized, valved connection to provide in-service access for insertion of an intrusive probe is not available, a system shutdown is usually necessary to install the probe in an existing nonvalved connection or to perform system modifications to install an access connection for insertion of the probe. In some instances, probe access connections have been installed by hot tapping the in-service system. A risk-based assessment of the hot tap, considering safety and reliability issues associated with the in-service welding, is typically performed. Nonintrusive pressure probes, also known as patch probes, consist of a stainless steel body machined to fit the exterior surface of the pipe or vessel. The probes are normally installed on the exterior surface of the pipe or vessel wall using clamps or adhesive to form a sealed cavity. The sealed cavity is connected to a pressure gauge and bleed valve directly or via capillary tubing (see Figure 2). In this case, some of the atomic hydrogen generated by reactions at the internal surface of the pipe or vessel wall permeates through the pipe or vessel wall into the sealed cavity and forms H2 gas that is registered as an increase in pressure by the pressure gauge. Nonintrusive probes have the ability to measure the hydrogen flux through the actual pipe or vessel wall material and are often more easily located at any orientation or location in a system. They assess the susceptibility of hydrogen-related damage if critical permeation conditions are known for this specific material; however, the sensitivity


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and time response to changes in the corrosive environment decrease significantly with increasing wall thickness. Type (1)—Vacuum Hydrogen Probes The vacuum hydrogen probes use vacuum-ion pumps to collect and measure hydrogen and are similar to pressure hydrogen probes that use H2 gas pressure as the monitored parameter. The measurement techniques used in vacuum hydrogen probes vary from straightforward vacuum loss measurement to sophisticated measuring instrumentation that typically provides sensitive and accurate measurements. The vacuum hydrogen probes are available in both intrusive and nonintrusive types. The most common type of vacuum hydrogen probe available, depicted in Figure 3, is similar to a nonintrusive-type pressure hydrogen probe (see Figure 2). However, once a vacuum hydrogen probe is installed, a vacuum is established in the probe cavity using a hand-held vacuum pump. The atomic hydrogen that diffuses through the pipe or vessel wall creates a loss in vacuum as H2 gas is formed within the cavity. The main advantage of this type of

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approach when compared to the pressure probes is increased sensitivity. It is difficult to ensure the absence of air leaks into the system for long periods of time, inducing measurement uncertainties, because a reduction in vacuum is often related not only to hydrogen ingress. A vacuum hydrogen probe that measures low partial pressures of H2 gas using a hydrogen ion gauge was developed by Lawrence.1 The hydrogen ion gauge consists of a palladium/silver (Pd/Ag) alloy window that is sealed in the chamber in which H2 gas is accumulated. The chamber is then charged with an inert gas to ensure only diffused hydrogen is detected at the gauge. The internally heated Pd/Ag alloy window allows hydrogen into the gauge. The accumulated hydrogen is ionized using an internal heater when the hydrogen partial pressure reaches a certain level (1 µPa).

Schematic of a nonintrusive, type (1) vacuum hydrogen probe.

Vacuum gauge

Relief valve

To vacuum pump

Capillary tubing

Stainless steel foil

Figure 3

A vacuum hydrogen probe that maintains a high vacuum in a cavity into which hydrogen permeates using a magnetic ion vacuum pump was developed by Radd and Oertle.2,3 The electrical current requirement of the pump is proportional to the rate at which hydrogen enters the cavity. Although this probe is extremely sensitive, the cavity normally supports a high vacuum (1 µPa), and a vacuum of 0.1 Pa is normally achieved before the magnetic ion pump is operated.

The two vacuum probes described above are typically used in laboratory environments because an external power source and other hardware are generally used in conjunction with these probes. Type (2)—Electrochemical Hydrogen Probes The electrochemical hydrogen probes are usually nonintrusive and are attached to the exterior surface of a pipe or vessel wall. They are subclassified as types (2A),


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(2B), and (2C) according to the degree of intimacy between the electrochemical sensor and the steel surface at which hydrogen measurement is of interest. At one extreme, in type (2A), the steel surface forms an electrode at which the arriving atomic hydrogen is oxidized, and hydrogen is sensed before H2 gas is formed. Type (2A)—Conventional Electrochemical Probes

Conventional electrochemical probes, occasionally known as Devanathan-type probes, are attached to the steel wall of the pipe or vessel to form an electrochemical cell, making the steel into an anode in contact with an electrolyte that is also in contact with an auxiliary or counter electrode.4,5 Hydrogen atoms diffuse from the test steel’s interior surface through the steel wall to the anodic interface at which oxidation occurs.

The electrical current normally used to sustain the oxidation reaction is proportional to the rate at which hydrogen atoms enter the anodic cell, specifically, the atomic hydrogen flux (flow per unit area). Because of difficulties with preparing and maintaining a well-defined steel surface, electrolyte impurities, and gas evolution, the Devanathan-type probe, while commonly and continuously in use in fundamental research studies, is not readily transferred to the field.

Type (2B)—Electrochemical Probes with Steel Surface Precoatings A hydrogen-permeable metal more noble than iron, such as nickel (Ni) or Pd, is often used as a steel coating with its external surface in contact with an electrolyte, as described above. This enables more aggressive anodic stripping of atomic hydrogen from a surface and concomitantly allows a wider range of electrolytes to be used. As with type (2A) probes, very careful surface preparation is normally performed before type (2B) probes are deployed. Allowance is normally given for permeability of the coatings used, unless the coatings are sufficiently thin.

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Type (2C)—Sealed Electrochemical Probes One means of ensuring some independence from steel surface conditions is using sealed electrochemical probes placed or pressed in close contact to a steel surface from which hydrogen permeation is to be measured. The essential difference between type (2C) sealed electrochemical probes and types (2A) and (2B) probes is that the permeable membrane is part of the type (2C) probe. Regardless of how intimate the contact is between the probe and the steel, with type 2C) probes, a portion of the H2 gas formed at the steel surface migrates between the steel and the Pd interlayer and then reabsorbs as atomic hydrogen in the Pd. An advantage of these probes is that they are readily movable and the constraint on steel surface preparation is relaxed. A disadvantage is that the Pd is normally thick enough to act as a structural barrier between the steel and electrolyte. Response to hydrogen is often slow and problems with respect to hydrogen concentration gradients across the various interfaces have been experienced. Examples of Type (2) Electrochemical Probes A schematic of a typical electrochemical hydrogen probe that normally uses a potentiostat for operation is shown in Figure 4.6,7 The probe consists of a chamber made from an insulator material that houses reference and auxiliary electrodes and a thin Pd foil (type [2B]). Similar probes of type (2A) and type (2C) are available. For hydrogen monitoring, the external surface of the pipe or vessel under study is cleaned, degreased, and coated with a thin layer of Pd, or Pd foil is placed on the surface and the chamber is mounted in place using mechanical straps. The chamber is then filled with the appropriate electrolyte. The electrolyte used is either concentrated sulfuric acid (H2SO4) or dilute sodium hydroxide (NaOH). The type (2A) probes use the external steel surface as the anode. The atomic hydrogen that enters the chamber is oxidized by an appropriate potential, and the oxidation current is monitored.


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Figure 4

Schematic of a type (2B) electrochemical hydrogen probe controlled by external circuitry.

Working electrode

Auxiliary electrode

Electrolyte Foil

Pipe or vessel wall

Reference electrode

Potentiostat

Berman, Beck, and DeLuccia developed a type (2A) probe based on fuel cell technology that eliminated the use of external circuitry required for applied oxidation potential in the anodic cell.8 They used a cell containing a nickel oxide (NiO) electrode in a NaOH electrolyte that functioned as a fuel cell. The NiO electrode maintained the steel surface at the desired anodic potential. In operation, the NiO electrode was connected electrically to the metal surface through a known resistor. The hydrogen atoms reaching

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the anodic cell were oxidized by the potential generated by the NiO electrode. The current developed in the circuit was measured, providing permeation rate data. Two type (2C) hydrogen probes based on the fuel cell principle are shown in Figures 5 and 6. The probe in Figure 5 consists of a cell containing a nickel/nickel oxide (Ni/NiO) electrode in a NaOH electrolyte that uses the exterior surface of the pipe or vessel under study as the anode. Another self-powered hydrogen probe is a sealed cell containing a metal oxide cathode and a palladized steel window (anode) in a NaOH electrolyte (Figure 6).


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Figure 5

Schematic of a self-powered, type (2C) electrochemical hydrogen probe.

Ni/NiO Electrode

Electrolyte

Ammeter

Vessel Wall
Figure 6
Schematic of a self-powered, type (2C) electrochemical hydrogen probe.

Palladized steel

Plastic seal

Electrolyte Metal oxide (cathode)

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A type (2B) hydrogen sensor based on battery cell technology has been developed.9-11 In this application, the porous electrode that was generally used in the anodic compartment of a traditional fuel cell was replaced by a metal permeable to atomic hydrogen. A schematic representation of the sensor consisting of a protonic exchange membrane (PEM) is shown in Figure 7. The

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atomic hydrogen emerging at the anodic surface is oxidized, and an equivalent amount of oxygen from the air is reduced. Consequently, a cell current that is proportional to the flux of atomic hydrogen that permeates through the steel and steel coating is obtained. The PEM does not use liquid electrolytes, has an extended lifetime, needs no external power, and is often adapted for use on steel at elevated temperatures up to 80 °C (176 °F).9

e-

Steel

H

Hydrogen Diffusion

Electrolyte(H+ transport)

Palladized Surface(2H 2H+ + 2e-)

Porous Electrode(1/2O2 + 2H+ + 2e- H2O)

Hydrogen Entrance

H+ Hads

Schematic representation of a fuel cell hydrogen sensor using a PEM.

Porous electrode (½O2 + 2H+ + 2e– H2O)

H+ Hads

Palladized Surface (2H 2H+ + 2e–)

Hydrogen entrance

Electrolyte (H+ transport)

Steel

H

Hydrogen diffusion

e

Figure 7

Type (3)—Hydrogen Collection Probes Hydrogen collection probes continuously collect hydrogen effluxing from a steel surface in a stream of air that is conveyed to a remote analyzer incorporating an amperometric hydrogen sensor.12,13 A schematic diagram of a monitoring system using a hydrogen collection probe is shown in Figure 8. The monitoring system is comprised of a hydrogen collector of well-defined geometry that is attached to steel to sweep the hydrogen effluxing from the steel surface into the well-defined air stream drawn into the suction of a low-voltage (e.g., battery-powered) pump.

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These probes have the ability to measure hydrogen efflux rapidly without recourse to extensive test surface preparation because an intimate seal is not normally used. The high sensitivity and reproducibility of this sensor response are achieved because of well-defined diffusion boundary conditions between the sensor surface and the sensing electrode of the amperometric cell at which hydrogen is efficiently oxidized, and thus, the concentration of hydrogen is practically zero. The sensor current is amplified and output either as an analog or digital signal. The monitoring system is capable of providing reliable measurement of hydrogen flux within 1 min to a resolution of ± 2 pL/cm2·s (1 pL = 10–9 cm3). The principle has been extended to use with steel surfaces at temperatures up to 300 °C (572 °F).


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Figure 8

Schematic of a monitoring system using a type (3) hydrogen collection probe.

Sensor

Collector

Pump

Exhaust

Direction of gas flow

Steel surface

Data output

Capillary

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Hydrogen Flux

The interpretation of data from various hydrogen monitors is not straightforward. The pressure/vacuum probes are cumulative devices that indicate an increase in pressure or decrease in vacuum with time as a result of accumulation of H2 gas in a known volume. The meaningful parameter, hydrogen flux, is normally calculated from the pressure versus time data. Electrochemical hydrogen probes provide an electrical current that is directly related to the flux of atomic hydrogen diffused through the surface. Type (1)—Pressure and Vacuum Hydrogen Probes The hydrogen flux, JH2

(µmol/cm2·d), in steady state

because of an increase in pressure or decrease in vacuum is given by Equation (1):

(1) Where: ∆P = increase in pressure or decrease in vacuum in time (t) (kPa) V = volume of the hydrogen probe (cm3) A = exposed surface area of the hydrogen probe (cm2) t = time between pressure or vacuum readings (h) T = absolute temperature during the test (K) R = gas constant (= 8.3144 × 10–3 kPa·cm3/K·µmol) Equation (1) is strictly valid at steady state because the

⎩⎨⎧

⎭⎬⎫×∆=

At(24)

RTP)V(

H

J2

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equations for the transients are sometimes more complex, depending on the presence of a capillary between the hydrogen collector (or probe cavity) and the pressure gauge.11,12 Type (2)—Electrochemical Hydrogen Probes The hydrogen flux, JH2

(µmol/cm2·d), corresponding to a

measured atomic hydrogen permeation current density, ip (µA/cm2), is often calculated in accordance with Faraday’s law using Equation (2):

( )24600,3 ××⎥⎥

⎦

⎤

⎢⎢

⎣

⎡=

2Fpi

HJ

2= 0.448 × ip (2)

Where: F = Faraday’s constant (96,500 C/mol) Type (3)—Hydrogen Collection Probes The flow of the air stream, f (Ncm3/s), across the steel surface is carefully regulated by means of restrictions and a flow bypass between the pump and sensor to ensure it is smooth and remains constant. The flux of hydrogen emanating from the steel, J (Ncm3/cm2·s), is given by Equation (3):


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J = (c × f ) /A (3) Where: A = the effective area over which hydrogen is captured (cm2) c = the concentration (volume fraction) of hydrogen in the air stream resulting from hydrogen entrainment (volume of hydrogen/volume of air stream)

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NOTE: Ncm3 designates the volume at normal (standard) temperature and pressure conditions.

References
1. S.C. Lawrence, Jr., “Hydrogen Detection Gauge,” in ASTM(1) STP 543, Hydrogen Embrittlement Testing (West Conshohocken, PA: ASTM, 1974). 2. B.E. Albright, “Development and Application of a New Hydrogen Sensing Instrument,” CORROSION/76, paper no. 42 (Houston, TX: NACE, 1976). 3. F.J. Radd, D.H Oertle, “Electronic Hydrogen Sensor Studies in the H2S-Air-NaCl-H2O-Fe Corrosion Systems,” MP 16, 10 (1977): p. 12. 4. M.A.V. Devanathan, Z. Starchurski, “The Absorption and Diffusion of Electrolytic Hydrogen in Palladium.” Proceedings of The Royal Society(2) (London, UK: The Royal Society, 1962), p. 90. 5. J. McBreen, L. Nanis, W. Beck, “A Method of Determination of the Permeation Rate of Hydrogen Through Metal Membranes,” Journal of Electrochemical Society 113, 11 (1966): p. 1218. 6. R.L. Martin, E.C. French, “Corrosion Monitoring in Sour Systems Using Electrochemical Hydrogen Patch Probes,” Journal of Petroleum Technology 20, 11 (1978): pp. 1566–1570. 7. R.L. Martin, “Inhibition of Hydrogen Permeation in Steels Corroding in Sour Fluids,” Corrosion 49, 8 (1993): pp. 694–701. 8. D.A. Berman, W. Beck, J.J. DeLuccia, “The Determination of Hydrogen in High Strength Steel Structures by an Electrochemical Technique,” Proceedings of the American Society for Metals Conference on Hydrogen in Metals (Materials Park, OH: ASM International,(3) 1973), pp. 595–607.
9. V.B. Baez, C. Mendez, J.R. Vera, “Non Intrusive Hydrogen Permeation Measurement Based on Fuel Cell Technology,” CORROSION/2000, paper no. 465 (Houston, TX: NACE, 2000). 10. O. Yepez, J.R. Vera, R. Callarotti, “A Comparison Between an Electrochemical and a Vacuum Loss Technique as Hydrogen Probes for Corrosion Monitoring,” CORROSION/97, paper no. 272 (Houston, TX: NACE, 1997). 11. J.R. Vera, O. Yépez, R. Callarotti, “Interpretation of Hydrogen Permeation Transients Obtained by the Vacuum Loss Technique,” CORROSION/98, paper no. 397 (Houston, TX: NACE, 1998). 12. R.D. Tems, F.W.H. Dean, “Field Application of a New, Portable, Non-Intrusive Hydrogen Monitor for Sour Service,” CORROSION/2000, paper no. 471 (Houston, TX: NACE, 2000). 13. R.D. Tems, A.L. Lewis, A.I. Abdulhadi, “Field and Laboratory Measurements with Hydrogen Permeation Devices,” CORROSION/2002, paper no. 345 (Houston, TX: NACE, 2002).

__________________________________________

(1) ASTM International (ASTM), 100 Barr Harbor Dr., West Conshohocken, PA 19428-2959. (2) The Royal Society, 6-9 Carlton House Terrace, London, UK SW1Y 5AG. (3) ASM International (ASM), 9639 Kinsman Rd., Materials Park, OH 44073-0002.


1c184-h2 permeation

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