Diffusible Hydrogen Measurement in Steel Welds Using an Electrochemical Hydrogen Sensor

Diffusible hydrogen (H_D) measurement in steel welding consumables having cellulose, rutile and basic coating has been carried out using a Proton Exchange Membrane Based Hydrogen Sensor (PEMHS). The sensor is an electrochemical fuel cell based device which uses Nafion@117 as proton exchange membrane electrolyte. This can detect hydrogen in an Ar+H₂ mixture with detectable limit of 1 ppm. Further, HD measurements have also been carried out on basic coated electrodes of modified 9Cr-1Mo steel, with very low levels of H_D content. Results obtained have been compared with those obtained from H_D measurement using mercury manometer as per standard ISO 3690. One to one correlation has been obtained between these two different methods of measurements. This sensor has shown good sensitivity, accuracy and precision hence is reliable for H_D measurement. In addition to the above measurement, this method was used to study hydrogen evolution from the weldments as a function of time. The paper presents and discusses the principles of H_D measurement using this sensor, its applications for H_D measurements in weldment, the results obtained, its application to study the hydrogen evolution from weldment as a function of time and the possibility of using this sensor for measurement of hydrogen evolved from the weld specimens at high temperatures.