Microbiological Influenced Corrosion (MIC) is a common cause of metallic failure and currently known as one of the important case in pipeline failure. Otherwise it was often found also in cooling water system, in the equipment of pulp and paper, and oil and gas industry. Certain bacteria have a wide range of life condition and can be found anywhere. Sulfate Reducing Bacteria (SRB) is a bacteria that was frequently found as a cause of corrosion in steel surface by creating pits. In this research, the corrosion test was done by using one species of SRB which is Desulfovibrio Baculatus. The water that contains bacteria growth medium (API Sulfate Broth) is used as a media for API 5L X65 steel corrosion test. Sulfate for the growing of SRB was added in the solution in 8.56 , 17.12 , 42.8 and 85.64 ppm concentration, and the immersion test was done during 1,7,14,21 days. The source of sulfate is FeSO4.7H2O, and this compound was considered also as a source of Iron (II). The result shows that the weight loss is increase with increasing of immersion period. Between 7-14 days of immersion time, the increase of weight loss that present a corrosion rate attains the highest condition and decrease again after a longer time of immersion period. Morphologic observation reveals that the corrosion product consists of Iron Oxide and biological deposits that were formed at the beginning of corrosion test, and continuing with the formation of Iron Sulfide at a longer period of immersion. The formation of Iron Sulfide was associated with the increase of corrosion rate. Keywords: MIC, SRB, Desulfovibrio Baculatus, Immersion, FeSO4 content.

Microbiological Influenced Corrosion (MIC) is a common cause of metallic failure and currently known as one of the important case in pipeline failure. Sulfate Reducing Bacteria (SRB) is a bacteria that frequently caused corrosion in steel surface by creating pits. In this research, the corrosion test was done by using one species of SRB which is Desulfovibrio Baculatus. The water that contains bacteria growth medium (API Sulfate Broth) is used as a media for API 5L X65 steel corrosion test. Sulfate for the growing of SRB was added in the solution for 8.56, 17.12, 42.8 and 85.64 ppm, and the immersion test was carried out for 1, 7, 14 and 21 days. The source of sulfate is FeSO4.7H2O, and this compound was also considered as a source of Iron (II). The result shows that the weight loss increased at 7 to14 days of immersion time with immersion period as well as the increase of FeSO4 content. But, it decrease after 14 days of immersion that represents a maximum weight loss attained at this moment. Morphologic observation revealed that the corrosion product consists of Iron Oxide and biological deposits that formed at the beginning of corrosion test, and after that, the formation of Iron Sulfide occurred were associated with the increase of corrosion rate. So, the increase of FeSO4 content as the SRB nutrition in the solution, gives a strong influence in the increasing of corrosion rate and formation of an unstable corrosion product.