Rectifier diode confusion for high power circuit

Hi all,
I put together an Arduino circuit for high power control like in the tutorial: http://bildr.org/2011/03/high-power-control-with-arduino-and-tip120/
Instead of using the TIP120 I used a MOSFET that allows much higher amps to be switched.
The circuit has been working fine for DC lamps/light bulbs but now I would like to connect a motor which draws around 20A at 12v.
To avoid voltage spikes flowing in the opposite direction, I read that a rectifier diode can be used.

Would something like this diode be strong enough to handle the load?:
http://www.fairchildsemi.com/ds/SB/SB560.pdf

I tried reading the datasheet but don't understand how to interpret the data. e.g. The diode is rated at 60v, Forward Current of 5A, Peak Forward Surge Current of 150A etc..

Thanks in advance

The diode needs to handle the full 20 Amps. (I think some MOSFETs have the diode built-in????)

With a 150 Amp peak surge current, it might be OK, but I'd say you are taking a risk unless you can measure the current over time and compare it to what's allowed by the diode specs.