Advances in reducing hydrogen effect of pipeline steels on hydrogen-blended natural gas transportation: A systematic review of mitigation strategies

Utilization and transportation of hydrogen energy are considered an inevitable trend toward achieving global zero CO2 emission. It is predicted that the utilization and storage of natural gas and hydrogen will be one of the hotspots in the coming years. With this aim, large-scale transportation of hydrogen-blended natural gas, which significantly reduces carbon emissions and gas transportation costs, serves as a prerequisite. However, with a covalent radius of 0.37 angstrom, the permeation of H atoms into pipeline steel is unavoidable, seriously threatening long-term service safety. The hydrogen effect (H-effect) processes, including physical/chemical adsorption, dissociation, and dissolution diffusion have long been studied for many years. Various materials improvements and environmental control procedures have been continuously applied to hinder the H-effect. This review focused on three aspects of H-effect elimination and how it affects material degradation. The microstructure strategies include elemental alloying and heat treatment, which can change the microstructure of pipeline steels. The surface treatments include shot peening and electroplating. Shot peening can lead to enhanced residual compressive stress and plastic deformation. Meanwhile, electroplating can be used in conjunction with shot peening. The last strategy, cathodic protection, is closely related to hydrogen concentration, temperature, microorganisms, alternating current and so on. Finally, the outlook of the H-effect of pipeline steels with consideration of marine and polar soil environments has been proposed. The aim of this review was to provide technical support for reducing the H-effect in hydrogen-blended natural gas transportation, so as to accelerate the realization of global zero CO2 emission.