A structural enclosure includes a pair of aluminum rails with an upper wall and a lower wall spaced apart from the upper wall, a plurality of sleeves extending into and captured within the aluminum rails, and each of the plurality of sleeves having a head with a predefined thickness disposed on an outer surface of the aluminum rails and configured to separate the outer surface of the aluminum rails from a steel vehicle chassis to which the aluminum rails are mounted. The structural enclosure can be an aluminum battery box for an electric vehicle and the aluminum battery box can be mounted to and electrochemically isolated from the steel vehicle chassis.