On off shores conditions, particularly in the field of construction that uses low-carbon steel material, often a metal corrosion due to a reaction with its environment. The most effective way to prevent corrosion is to isolate the corrosion rate of a metal that is happening can be hampered. The use of green inhibitors that are environmentally friendly, biodegradable, and has a relatively low price to the alternative options to achieve that goal. Sarang semut extract is one of the organic material that can be used as green inhibitor on low carbon steel in 3.5% NaCl environment with a variety of concentrations used was without inhibitor, 100, 200, 300, 400, and 500 mg/l. Test methods used are weight loss and potentiodynamic polarization to determine the effectiveness of the inhibition. Based on the research that has been conducted corrosion rate decreases occurred with increasing Sarang Semut extract. Greatest efficiency at a concentration of 500 mg/l inhibitor of 68.94%. That is because the Sarang Semut extract shown to contain N and O elements that can form complex compounds with metals that can inhibite metal surface.