ive done lots of gold plating and rhodium plating over the years and ive always used this process:
1. Clean the piece (ultrasonic)
2.Then rinse in clean water
3. Put into salts to de grease it of any further grease etc.
4. Then after salts rinse in clean water again.
5. Then Dip into de-ironised water
6.Then straight into plating solution and then rinse.
Ive not had any problems so far.
It seems alot but it seems to work for me. hope this helps.