When I purge bare hard drives I like to use their built in Secure Erase feature. Can I use the same feature if I have the same drive in an external USB box with SATA- USB bridge board?
It is possible to do so, but it is a very, very, very bad idea.
The Secure Erase command disconnects the drive from the system and offloads all erase commands to the drive controller. The drive controller will not communicate with the host system until the erase command has been completed. The drive must be left alone for the duration of the erasure. SATA/PATA ports have no problem doing this (they're designed with it in mind), the ATA-USB bridge used by external enclosures is not. If the hard disk controller stops responding (which it will during the erase command) the USB host controller will not be expecting the device to timeout and disconnect. The host controller may attempt to disconnect or reset the bridge device, which can interfere with the hard disk controller while it is performing the secure erase. This can cause undefined behaviour on the drive, including unrecoverable failure.
If you want to erase an external drive connected over a USB or Firewire bridge you must use a software method of erasing the drive. If the drive is an SSD it must be connected to a SATA port and erased using the secure erase command.