Caffeine was water extracted from byproduct of green tea, as old leaves, using H2O-MeOH solution, and purified up to 99 percent. Corrosion inhibition of the extracted caffeine, for the mild steel in acid solution, was examined using electrochemical methods: corrosion measurement, impedance measurement. The obtained results show that the inhibition efficiency was achieved over 95 percent (belong to the concentration). Inhibition mechanism has been discussed
caffeine was adsorbed on the steel surface forming barrier films capable to decrease an attack of the aggressive solution. In this case, the extracted caffeine can be applied as a corrosion inhibitor in solutions for rust cleaning, descaling and surface treatment.