What Does Hydrogen Probe Mean?
A hydrogen probe is designed to measure the permeation rate of atomic hydrogen (H+) (measured as hydrogen gas (H2)) associated with hydrogen-induced cracking. It collects the hydrogen formed on the surface and gives a signal related to amount permeated.
Hydrogen probes are useful in measuring the flow rate of atomic hydrogen generated from corrosion which passes through steel, and gives rise to hydrogen-induced corrosion (HIC) problems and hydrogen blistering.
A hydrogen probe system entails:
- Relatively simple construction
- Rapid installation at any location
- Trouble-free operation for extended periods of time without supervision
Corrosionpedia Explains Hydrogen Probe
A hydrogen probe provides useful information about changes in the corrosive environment in processes where HIC is present or could occur. This can occur in cathodic reactions in acid solutions, particularly in the presence of hydrogen sulfide.
Hydrogen probes are composed of three components:
- Measuring head
- Hollow plug assembly (retrievable) or probe body (fixed)
- Sensing element comprised of a thin-walled tube, designed to simulate a material delamination or inclusion
Hydrogen probes are available in retrievable, retractable or fixed designs, and measuring heads are available in either electronic or mechanical forms.
When the hydrogen-sensing element in the process stream begins corroding, hydrogen generated by the corrosion reaction permeates through the wall of the tube. Measuring the pressure in the tube indicates hydrogen buildup; the rate of pressure increase is proportional to the corrosion rate.
If pressure accumulates at a certain rate per day and then increases by a factor of 10, this indicates a significant change that should be addressed. Hydrogen probe readings, however, have not been found to be suitable for direct determination of corrosion rate, only of changes in the process, and it is recommended that they be applied carefully as part of a complete corrosion control program in applications where HIC is a concern.