Linking NACE test results to H-pick up and permeation in the presence of H2S

To understand the effect of sour conditions on the embrittlement phenomena during NACE testing, permeation measurements in H2S environment have been installed and validated at OCAS. Now that the methodology is available we are ready to focus on the material aspects and investigate metallurgical parameters.

A series of laboratory mechanical testing is described in NACE TM0177 for evaluating resistance to cracking failure in low-pH aqueous environments containing H2S.  Since hydrogen embrittlement and the resulting cracking phenomena are closely related to the hydrogen pick-up and transport in steels, it is crucial to closely monitor these phenomena during testing in NACE environments.

For those purposes, a fast extraction device is available for “in-situ” sampling, allowing H pick-up to be accurately measured over time. Also, the dedicated permeation cell is now available for testing with and without applied stress in NACE environment. As such, the effect of the passive layer that is formed in this environment can be taken into account in the testing. The influence of experimental parameters such as pH and H2S partial pressure (PH2S) has been investigated in detail for acceptance of the test set-up. The methodology is now validated, so can now be used for what it was meant for, i.e. the study of metallurgical influences.

“We’re conducting permeation under tension to understand the combined effect of sour conditions and applied stress. The methodology is ready, we can now proceed with screening different materials.”

Krista Van den Bergh, Senior Research Engineer Surfaces, OCAS