Menu

HydrogenPermeability

Hydrogen embrittlement (HE) also known as hydrogen assisted cracking (HAC) and hydrogen-induced cracking (HIC), describes the embrittling of metal after being exposed to hydrogen . It is a complex process that is not completely understood because of the variety and complexity of mechanisms that can lead to embrittlement. Mechanisms that have been proposed to explain embrittlement include the formation of brittle hydrides, the creation of voids that can lead to bubbles and pressure build-up within a material and enhanced decohesion or localised plasticity that assist in the propagation of cracks.[2]

For hydrogen embrittlement to occur, a combination of three conditions are required:

  1. the presence and diffusion of hydrogen
  2. a susceptible material
  3. stress

Hydrogen is often introduced during manufacture from operations such as forming, coating, plating or cleaning. Hydrogen may also be introduced over time (external embrittlement) through environmental exposure (soils and chemicals, including water), corrosion processes (especially galvanic corrosion and acidic corrosion) including corrosion of a coating and cathodic protection . The following photos shows the effect of hydrogen on fracture surface (on the left ) of otherwise  a ductile material(on right)

We can measure hydrogen permeability by two ASTM methods. We can perform the hydrogen permeability measurement at your facility.
The charging hydrogen (input) will be the responsibility of the client. We will measure the hydrogen permeating on the external side of the tank by electrochemical technique or change in the pressure.
We recommend three thicknesses of polymer for permeability study.. This will confirm the rate determining step (RDS) is indeed diffusion of hydrogen through the polymer lining.

Matergenics  performs hydrogen permeation testing per ASTM G148This electrochemical technique for evaluation of hydrogen uptake, permeation, and transport in metals is based on the work of Devanathan and Stachurski.

The procedures described in ASTM G148, can be used to evaluate the severity of hydrogen charging of a material produced by exposure to corrosive environments or by cathodic polarization. It can also be used to determine fundamental properties of materials in terms of hydrogen diffusion (for example, diffusivity of hydrogen) and the effects of metallurgical, processing, and environmental variables on diffusion of hydrogen in metals.

The data obtained from hydrogen permeation tests can be combined with other tests related to hydrogen embrittlement or hydrogen induced cracking to ascertain critical levels of hydrogen flux or hydrogen content in the material for cracking to occur.

Electrochemical Hydrogen Permeation Testing Requirements

Hydrogen permeation testing is a complex process that requires the following if the results are to be reliable:

1-Reproducibility

2-Should be diffusion controlled and not surface controlled

3-If diffusivity and barrier properties are of interest, both surfaces should be coated with palladium to prevent oxide formation to control the permeation process. The surfaces should be free of oxides prior to coating palladium

4-Proof for diffusion controlled process is to plot 1/L vs steady state permeation for three coating thickness.

 

img_1426_large

Significance and Use

The procedures described, herein, can be used to evaluate the severity of hydrogen charging of a material produced by exposure to corrosive environments or by cathodic polarization. It can also be used to determine fundamental properties of materials in terms of hydrogen diffusion (for example, diffusivity of hydrogen) and the effects of metallurgical, processing, and environmental variables on diffusion of hydrogen in metals.

The data obtained from hydrogen permeation tests can be combined with other tests related to hydrogen embrittlement or hydrogen induced cracking to ascertain critical levels of hydrogen flux or hydrogen content in the material for cracking to occur.

 

hydrogen_permeation_2_large

1. Scope

1.1 This practice gives a procedure for the evaluation of hydrogen uptake, permeation, and transport in metals using an electrochemical technique which was developed by Devanathan and Stachurski. While this practice is primarily intended for laboratory use, such measurements have been conducted in field or plant applications. Therefore, with proper adaptations, this practice can also be applied to such situations.

1.2 This practice describes calculation of an effective diffusivity of hydrogen atoms in a metal and for distinguishing reversible and irreversible trapping.

1.3 This practice specifies the method for evaluating hydrogen uptake in metals based on the steady-state hydrogen flux.

1.4 This practice gives guidance on preparation of specimens, control and monitoring of the environmental variables, test procedures, and possible analyses of results.

1.5 This practice can be applied in principle to all metals and alloys which have a high solubility for hydrogen, and for which the hydrogen permeation is measurable. This method can be used to rank the relative aggressivity of different environments in terms of the hydrogen uptake of the exposed metal.

1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

hydrogen_permeation_nist_large

We are here to help

We respond to all customers promptly by sending a technical proposal to address testing, investigation and the proposal costs. If we need more information, our engineers will contact you.

Whether you are a large corporation or a small enterprise, we will provide you with the attention you need and deserve. In so doing, we hope to work with you for many years to come.

Please call Dr. Zee at 1-855-860-8759 and let us know how we can assist you in your investigation. Alternatively, you can send your request to info@matergenics.com.

Looking forward to hearing from you!

 

we_hare_here_to_help_you_large

Hear from Us

Stay up to date with our services by subscribing to our extremely cool, yet very infrequent newsletters.

No spam, ever. That is a promise.