This articles discusses the passivation process for purified water or WFI in pharmaceuticals
Passivation
It is the process where the protective outer layer on steel surface which is removed during welding is re-established by forming a barrier between interior surface of loop and free ion.
As purified water has an acidic pH thereby it necessitates the process of passivation of stainless steel to raise its resistance.
The tank is collected with 600 litres of purified water and later 20litres of 69% of nitric acid is added. The solution is later drained after recirculating for 30min.
In the next step the tank is collected with 600 litres of purified water and 25kgs of 100% citric acid is added which is drained after recirculating for 30min.
The circulation loop is flushed with purified water until the pH attains the value of 7.0 and no traces of sodium hydroxide or nitric acid should be present.
Related documents
http://documents.mx/documents/cleaning-and-disinfection-of-loop-after-installation.html.
Passivation of water for injection or purified water, wfi, nitric acid, sodium hydroxide
