Using aluminium enclosure as heat sink
Could aluminium oxide accumulate over time, increasing the resistance to unsafe levels?


There are some precautions to could be taken like coating the aluminum screw point with Alnox right after scrubbing it but before making the connection. This is up to US Gov standards http://www.usbr.gov/power/data/fist/fist3_3/vol3-3.pdf (see chapter 6).