Properly passivated stainless steel will not plate unless contacted by a plating part or the bath is not properly maintained. They must be passivated from time to time according to the procedures established (by STI) for safety and effective passivation without contaminating the solutions or rinse tanks. Stainless steel is composed of iron (Fe); nickel (Ni); chromium (Cr) and several other minor components. Stainless steel is not resistant to chemical or physical attack. The corrosion resistance of stainless steel depends on the formation of a ‘passive surface film’ composed of nickel and chromium oxides (Cr2O3 & Ni0).

Procedure:

1. Pump bath out into the corresponding drums, tote, or tank.

2. Spray rinse the tank & plumbing, then drain any leftover bath into corresponding drums or tank.

3. Pump in 40% Nitric for Passivation from the tote into empty tank.

4. Once tank is filled with “40% Nitric for Passivation” do the following 3 things.

A. Turn on all pumps to tank.

B. Set temperature of the “40% Nitric for Passivation” to 90o F.

C. After you have completed Set 1 and 2 set timer for 3 hours.

5. After 3 hours are up, unplug all pumps in the tank and turn off steam,

6. Pump “40% Nitric or Passivation” into the tote.

7. Drain any leftover Nitric into a bucket through the valve behind the tank and pour back into tote.

8. Spray rinse the tank and plumbing, then drain straight to the trench.

9. Fill empty tank with city water.

10. After the tank is filled with city water do the following 3 things.

A. Turn on all pumps to tank

B. Turn on air agitation

C. Add 2000 mls of NH4OH to neutralize water (per 100 gallons of water)

11. Let mix for 10 mins.

12. Pump water back into the tote unless instructed otherwise.

13. Spray rinse the tank and plumbing, then drain straight to the trench.

14. Take out spargers and clean in tank.

15. Thoroughly spray clean tank (Walls, Plumbing, Backflush, Etc.)

16. Once tank has been thoroughly cleaned reattach spargers back onto the reactor.

17. Spray rinse the entire tank with DI water one last time.

18. The tank has now been successfully passivated & cleaned and is now ready for a bath to be pumped in or made up new after the valve is closed.