Room Temperature Synthesis of Hydrogen Permeation Barrier for Storage and Transportation Application

Distribution of hydrogen in future hydrogen-based economy requires a dense pipeline network for its safe delivery. Natural take is to consider the existing networks of natural gas (NG) infrastructure. However, the main issue is that hydrogen-embrittlement on NG pipes’ steels significantly reduces their fracture toughness and threatens their structural integrity 1 . Besides developing a new grade of steels less susceptible to the embrittlement, effective hydrogen permeation barriers (HPBs) remain important solution for re-purposing of the existing NG infrastructure for hydrogen transport. Besides a few specific metals, candidates are some oxides,carbides, and nitrides. These coatings require extreme conditions for their synthesis, which renders their application impractical. We employed strategy for HPB synthesis based on electroless Cu-deposition process 2 . We have employ solution chemistries exploring a wide range of reducing agents. These include formaldehyde, glyoxylic acid, Na 2 HPO 2 ... and others. Variety of complexing agents were considered as well; EDTA, sodium citrate, sodium potassium tartarate and others. Our optimum solution design favored a large driving force for Cu reduction providing high nucleation rates and films with fewer defects and dense grain boundaries. The comparative analysis between hydrogen permeation rates through bare steel samples and steel samples coated with Cu HPB films is performed using Devanathan - Stachurski permeation technique 3 . The Cu-HPB thickness varied from experiment to experiment. More than 30 samples have been evaluated. An integral example of these measurements is shown in Figure 1. Permeation reduction factor (PRF) for Cu-HPB as a function of the ratio between steel and Cu-HPB thickness is shown against theoretical calculations. Our results exceed theoretical predictions by factor of 2-5. Figure 1 : Calculations for PRF of Cu/(AISI 4340 steel) as a function of d s /d f ratio. Square, circular, and triangular dots represent PRF measurements for Cu-HPB/(ASTM A36 steel) samples produced from tartaric acid (TA) and EDTA solutions. Insets show optical images of steel and Cu/steel samples (left) and SEM of Cu surface morphology (right). References: Nemanic, Hydrogen permeation barriers: Basic requirements, materials selection, deposition methods, and quality evaluation, Nuclear Materials and Energy, 19 (2019) 451-457. Paunovic, Chapter 17: Electroless Deposition of Copper, in Modern Electroplating, fifth Edition , Eds, M. Schelsinger and M. Paunovic, Willey, NY (2005), p. 433. Iyer, R.N., Pickering, H.V., 1990. Mechanism and kinetics of electrochemical hydrogen entry and degradation of metallic systems. Annu. Mater . Sci . 20 , 299-338. Figure 1