New Developments in Atomic Hydrogen Permeation Measurements Using a Bimetallic Sensor

Hydrogen is becoming an important issue due to its characteristics and future applications as it opens access to a broad range of primary energy sources, including fossil fuels, nuclear energy and increasingly renewable energy sources (e.g. wind, solar and biomass) as they become more widely available. Hydrogen in fuel cells can be generated from hydrocarbons, usually alcohols, naphtas or natural gas. In this condition, hydrogen is the desired product. Unfortunately, systems dealing with hydrogen and some hydrocarbons often suffer from hydrogen damage. These damages include: hydrogen induced cracking (HIC), blistering, sulfur stress cracking (SSC) or stress oriented hydrogen induced cracking (SOHIC). These damages are also easily found in corrosive processes at equipments and pipes used in petroleum refining processes and petrochemical plants. The hydrogen, at these processes, is produced by acid media (H⁺) or chemical processes leading to protons formation (corrosion). The main problem is how to detect, in a safe, fast and economically feasible way, the formation of hydrogen — in this case, an undesirable product. For this work, it was built a cell for hydrogen permeation to study and evaluate a new sensor for atomic hydrogen permeating through a metallic wall. This new sensor is composed of two parts, each one build with a couple of dissimilar materials, being one a sensor couple, for hydrogen flux measurements, and a reference couple, for compensation of temperature variations. The results obtained showed good agreement between the Devanathan-Stachurski Cell (DSC) and the Bimetallic Sensor (BS) (Correˆa, 1999). Both sensors had a sharp increase in current or potential, for DSC and BS, respectively, when the charging side of the permeation cell was polarized. Both sides in the permeation cell were filled with 0.1 M NaOH (continuous N₂ bubbling) and the generation side polarized cathodicaly at 3 mA/cm². The peak potential for the BS was about 30 μV, obtained 12 to 15 h after the polarization.