The inhibition of carbon steel corrosion by extract of Allium Ampeloprasum was studied by weight loss method. The inhibition efficiency of the inhibitor was found to increase with increasing content of the extract. Inhibition efficiency of 98.3% was achieved with 40% v/v of the extract in 1M
hydrochloric acid during 3 hours at 25℃. Effect of temperature was also investigated and activation parameters were evaluated.