Nanoscale nickel is prepared from ethanol extracts of Allium cepa and characterized. Zerovalent face centred cubic (fcc) nickel nanoparticles oriented mainly at Ni (111) plane formed rapidly within 30-45 min. The nanoparticles are stabilized by negative surface potential, non-agglomerated, monodispersed, round-shaped and distributed between sizes of 39.5-53.1 nm. The nanoparticles are used to simultaneously regulate the rates of hydrogen gas production and X80 steel corrosion in 1 M HCl solution for the first time. The nanoparticles efficiently inhibit hydrogen gas evolution and X80 steel corrosion rates especially at increased concentration. Inhibition efficiency increases as temperature increases from 303 to 323 K, remains fairly constant from 323 to 343 K and decreases drastically from 343 to 363 K. By means of O-H, N-H and C=C sites, the nanoparticles are spontaneously physically adsorbed on X80 steel surface and act as mixed type corrosion inhibitor with dominant influence on cathodic reaction involving hydrogen gas evolution. In the presence of the nanoparticles, surface roughness (measured by AFM) reduces by 76.0% and heights of peaks from the mean plane reduces by 58.2%. Comparatively, even 100 ppm of the nanoparticles showed higher inhibition efficiency at all temperatures than 1000 ppm concentration of the crude extract. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.