Research On Properties Of Electrochemical Hydrogen Permeation Sensor

Hydrogen is generated by corrosion of metals exposed to process streams orduring the chemical cleaning of industrial equipment. A portion of such hydrogen canbe absorbed into the metal in a variety ways leading hydrogen damage. One of themost important safety concerns in the oil and gas industry is so-called H2S corrosion.For long-term operation under high temperature and high pressure environment thehydrogenation reactor is easy to generate hydrogen corrosion. In the presence of H2S,hydrogen generated by corrosion reactions could be easily absorbed and severelypermeated into the metal, leading to hydrogen damage. Since the important role ofhydrogen in the catastrophic failure of metal has been recognized, it is necessary todevelop on-line hydrogen permeation probes used in the industry to prevent frompremature component failures or to monitor the efficacy of anticorrosive measures.The principle, design, construction and performance of the amperometric andpotentiometric sensors to measure the permeation rate of hydrogen through the wall ofmetal equipment were investigated in order to develop a new type of hydrogen sensorwith high accuracy in this work. The hydrogen permeability experiments ofcommercial iron were measured by electrochemical technology at room temperature.The transient curves of hydrogen permeation under a given charging condition wereemployed to evaluate the performance of two types of hydrogen sensors. Comparedthe two performance indexes by experiments, we analyzed the feasibility and accuracyof the two monitoring methods in detail. The results presented in this paper are veryimportant on the selection of the optimal hydrogen sensor for a specific application.The results were shown as follows:1. The smooth, uniform and compact Ni coating was obtained via plating for5minutes at room temperature by1.00A dm2of current density. The optimumpotential of hydrogen oxidation on Ni coating was identified as0.350.05VNi. In thehydrogen permeation experiment, it was noted that the response time became shorterand the steady-state current gradually increased with temperature elevating. Thehydrogen diffusion time in iron traps delayed from the cathode side to the anodeside of the sample. The apparent diffusion coefficient of hydrogen was also decreasedseverely owing to the trapping of hydrogen and at last can making the response speedof the hydrogen sensor slow down. 2. Both amperometric type and potentiometric type of sensors could be successfulin the measurement of hydrogen permeation. The relative deviation of themeasurement results was3.0-13%.3. After five cycles of charging on and off, two types of hydrogen sensor exhibiteda good stability and reproducibility. The E-sensor has longer response time and lowersensitivity. The performance of I-sensor is more superior, so it can be used formonitoring equipment for a long time.4. A precursor of BaZr_0.4Ce_0.4Y_0.2O_3-αelectrolytes was synthesized by sol-gelmethod at sintered temperature which were150²50℃lower than that by solid statereaction. In order to solving the installation problem of amperometric hydrogen sensor,we pointed out the idea on the development of amperometric sensor composed of akind of proton conductor adhesives which contains two functions of high electricalconductivity and a strong adhesion. It is also a promising solid electrolyte used for thehydrogen sensor at high temperature.