The effect of ascorbic acid (AA) on the corrosion of mild steel in sulphuric acid solution has been investigated by open circuit potential (OCP) and polarization measurements. AA was observed to shift the OCP to more positive potentials with increasing concentration. The polarization curves revealed that AA inhibited the anodic metal dissolution reaction, although this effect became negligible at high anodic overpotentials. The trend of inhibition efficiency with concentration showed that efficiency increased rapidly at low concentrations, remained almost steady at intermediate concentrations and increased again at high concentrations. The mechanism of inhibition was considered in terms of initial chemisorption of AA according to the Temkin isotherm, followed by formation of chelate compounds with Fe2+ ions at high concentrations. EDS and AFM analyses of the electrode surface support the proposed inhibition mechanisms.