During construction or refurbishment of crude oil tanks, hydrotesting is routinely performed, sometimes with an aluminum floating roof or pontoons in place. Upon occasion, damage has been sustained to the aluminum floating roofs in a relatively short period of time. Damage is commonly believed to be a result of poor water quality with bacteria or chlorides being suspected of causing the corrosion. Galvanic coupling between the roof and the carbon steel tank has also been cited as a potential contributing factor. Experiments were set up using three types of aluminum alloys: AA 3003, AA 5052-H32 and AA 6061. The objective of the study was to replicate some common field conditions and to determine which mechanism could be the primary cause of damage; chlorides, bacteria or galvanic coupling. It is possible that the damage mechanisms act in concert, creating early life damage / failures. This paper shares some details from case studies on existing tanks and the results of the lab work to help pinpoint and identify the primary cause of such failures. The goal of this project was to approach this problem holistically.