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Investigation of H Microbiologically Infuenced Corrosion in Pipeline Hydrotesting Using Seawater ydrotesting is a common practice to assess pipeline integrity before service. Different from pneumatic testing that is used only for leak testing, hydrotesting is applied to test for both leaks and strength. During hydrotesting, a pipeline is flled with a liquid and pressurized to a pressure (usually 10%) greater than the anticipated future operating pressure. Background In general, hydrotesting itself lasts only eight to 10 h. In the oil and gas industry, however, it is often the case that water is left in the system afterward for many months before the system is actually commissioned. During this holding time or when the pipeline is frst exposed to an aqueous environment like wet lay-up, corrosion due to microbiologically infuenced corrosion (MIC) can commence.1 When the system makes contact with the ground2 or is even exposed to air,3 there are further possibilities for microbial contamination. Reuse of water also Kaili Zhao and Tingyue gu, Ohio University, Athens, Ohio increases chances for MIC. Improper ivan CruZ, Saudi Aramco, Dhahran, Saudi Arabia hydrotesting practices can cause MIC ardjan KopliKu, BP America, Inc., Houston, Texas pitting attacks and also black powder problems.4 MIC pitting during hydrotest itself may not be a big problem because of the limited hydrotest time frame. The biofilms left behind during hydrotest, however, may present a serious threat once the pipelines become operational, because fuids transported in pipelines may contain suffcient nutrients for bioflms to fourish and a pipeline is often expected to be operational for several decades. Tis work investigated the microbiologically infuenced corrosion (MIC) threat in pipeline hydrotesting using ofshore seawater samples for coupon tests in anaerobic vials. Longer-term sulfate- reducing bacteria pitting was predicted using a MIC prediction software program calibrated with short-term pitting data from the tests. 64 MATERIALS PERFORMANCE May 2013 Seawater in Pipelines Seawater is routinely used in the hydrotesting of subsea pipelines. Occasionally, other water sources may be used and they mainly come from aquifer water and/or produced water. Any water source for hydrotesting can contain miNACE International, Vol. 52, No. 5