The impact of some factors (such as inhibitor concentration, solution temperature, I- ions addition, surface finishing and immersion time) on the inhibitory action of radish seeds aqueous extract (RSAE) for mild steel corrosion in 1 M H2SO4 solution was investigated by using electrochemical measurements. The inhibition efficiency of RSAE increases with the increase of its concentration but decreases drastically at relatively high temperatures (50 degrees C). The addition of I- ions synergistically increased the inhibition efficiency of RSAE and this synergistic effect depends on the concentration of both inhibitor and I- ions. It was found that the inhibition efficiency of RSAE increases with a surface roughness of up to 400 grits after which it decreases with additional increases in surface roughness. The data revealed that the inhibition efficiency of RSAE increases with increasing immersion time in the tested solution which may be attributed to a slow rate of adsorption process. The inhibitory action of RSAE is suggested to be due the synergistic effect of its constituents. (C) 2011 Elsevier B.V. All rights reserved.