Corrosion is the process of natural changes in the nature of a material due to the influence or reaction with the surrounding environment. One way to control it is by adding inhibitors. In this study, seeds from guava (Psidium Guajava) were used as organic inhibitors. The test material used is API 5L grade B steel. For corrosive media, a solution of 1 M H2SO4 is used. In experiments used variations in the concentration of extracts 0, 2, 3, 4, 5 and 6 ml. The results of the experiments showed a decrease in the corrosion rate of API 5L grade B when there were additional inhibitors. This is supported by the experimental results of Potentiodynamic Polarization. The best concentration when achieving the highest inhibitor efficiency is when adding 5 ml. For polarization method, the corrosion rate when absence inhibitors show 75,018 mmpy and when presence inhibitor 2,8845 mmpy. Based on the calculation, the inhibition efficiency is 96.155%. This is also indicated by the results of weight loss measurement, the efficiency shown is 90.130%.