The Effluent Treatment Facility (ETF) at the Hanford nuclear-waste storage site is a waste treatment
facility that removes radioactive and hazardous contaminants from various sources. The facility
processes substantially more dilute waste that has lower pH values than the waste found in the tank
farms. The Secondary Waste Receiving Tank B (SWRT-B) at the ETF exhibited corrosion attack on the
tank ceiling and upper wall during recent inspections and this paper presents the results of laboratory
investigations performed to evaluate whether the in-tank additions of sulfuric acid that are made to adjust
waste pH are a possible cause for the corrosion attack. Laboratory testing was conducted to evaluate
the susceptibility of 304H stainless steel (UNS S30409), including in the sensitized condition to
investigate microstructural differences in welded regions, to H2SO4 vapor corrosion or splash-back
corrosion. The results of electrochemical testing indicate that as-received 304H showed no susceptibility
to corrosion in 4% H2SO4 even when anodically polarized while sensitized 304H exhibited corrosion at
open circuit conditions. A kettle test designed to simulate the addition of H2SO4 to the SWRT-B to
investigate acid vapor and splash-back corrosion was unable to replicate the corrosion observed in the
tank.