The presence of sludge-like deposits and interstitial liquid may create susceptibility to underdeposit corrosion in high-level waste tanks. As the sludge deposits form occluded regions or crevices with the tank bottom, the chemistry of interstitial liquid could become sufficiently aggressive to promote accelerated localized corrosion around or beneath the sludge deposits. This work seeks to evaluate the conditions necessary for underdeposit corrosion to occur and the nature of attack utilizing short term electrochemical techniques. Carbon steel coupons were exposed to a matrix of varying sludge conditions including wet sludge, compressed wet sludge, and dried, adherent sludge deposits to determine the conditions under which susceptibility to underdeposit corrosion exists. During the exposure, a number of electrochemical techniques were utilized to evaluate the susceptibility to underdeposit corrosion, including open circuit potential monitoring, linear polarization, electrochemical impedance spectroscopy, and potentiodynamic polarization. In addition, coupons were evaluated post exposure using laser confocal microscopy to evaluate the extent and nature of underdeposit attack.