  We present a polarization and Faraday rotation study of the hybrid morphology
radio galaxy NGC 612 (PKS 0131-36), using Australian Telescope Compact Array
observations from 1 to 3 GHz. In general, the results are consistent with an
external Faraday screen close to the radio source. In the eastern FRII lobe,
the RM of the hotspot increases in magnitude towards the leading edge, as well
as changing sign (compared to the rest of the lobe). The Faraday depolarization
is also ~3 times larger at the hotspot than elsewhere. A plausible explanation
for this is significant compression of ambient magnetised gas by the bow shock
produced by the advancing hotspot. The western FRI lobe also exhibits some
evidence of interaction with local magnetised gas, as a transverse band of high
RM coincides with a distinct bend in the lobe. Previous observations of NGC 612
revealed an HI bridge of tidal debris along the direction of the eastern lobe
towards the gas-rich companion NGC 619. We find no clear evidence that ionised
gas associated with this bridge is either mixing with or lies in the foreground
of the radio source. This is consistent with the absence of HI absorption
against the hotspot, and indicates that the tidal debris must lie mostly behind
the eastern lobe.
