One needs to be practical.
Standard diodes are good for 1KHZ without any problems,
With 6 amp current, the spike pulse is 1000 Hz at 6 amps with a duty cycle of around 5 microseconds out of 2 milliseconds.
Though one can use Schottky if they are 30 volts it is just a more difficult to find than a Silicon.
Also, you can use, a regular 5 to 10 watts transistor, tie the base to the emitter ( becomes the Cathode) then Collector is the Anode and one can attain the same results, make sure that the NPN transistor is at least 30 volts breakdown.
A PNP power transistor, if used, the emitter becomes the Anode and the Collector the cathode.
Nando