Ultrasonic surface modification of mild steel for corrosion protection

The basic corrosion properties of mild steel can be changed or modified by applying a series of operation on its surface. We followed the following sequence for surface modification:
1) Ultrasonic surface modification: Using ultrasonic
machine(Oscar ultrasonic processor), we ultrasonicated for half hour, with a pulse time of 2 seconds.
2) Ultrasonic bath phosphating/ tungstating: Sample was
treated in ultrasonic bath for 15 or 30 minutes(as required/directed) and phosphating/ tungstating is done
ie an intermediate coating was applied.
3) Sample was dried, blocked, and potentiodyanamically
tested to compare the corrosion properties(using the
datas of corrosion potential and current) with some
intermediate sample specific steps sometimes.