The hydrogen permeation analysis during the corrosion of stainless in pickling acid such as 2N H3PO4 in the presence and absence of an ecofriendly inhibitor 6R,7R)-7-{[(2R)-2-amino-2-(1-cyclohexa-1,4-dienyl)acetyl]amino}-3-methyl-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid has been cariedout using weight loss, gasometric and electrochemical studies. The antibiotic seems to be more effective in reducing the dissolution of steel in 2N H3PO4Potentiodynamic polarization clearly indicated that the inhibitor follows mixed mode of inhibition in 2N H3PO4. Hydrogen permeation and EIS measurements have confirmed that the present antibiotic retards the corrosion of SS 304 effectively in pickling acid. The theoretical values of EHOMO, ELUMO, ΔE and dipole moment in the presence of inhibitor confirmed its effective adsorption on SS 304 surface. © 2015, Sphinx Knowledge House. All rights Reserved.