Do I need to passivate following complete or partial electropolishing?
A. Many believe electropolishing alone provides a passivated surface. They argue that during the electropolishing process oxygen is concentrated on the surface due to the nature of the electrochemical process and that this presence of oxygen along with metal removal with a phosphoric acid based electrolyte provides the very best “passivated” surface. Testing for additional release of “free iron” from a completed electropolished and rinsed vessel by circulating and analysing heated nitric acid solution shows no increase in “free iron” release indicating the electropolished surface is as passivated as possible. ASTM B912 recognizes electropolishing as a suitable form of passivation as long as a citric acid or nitric acid flush is performed between the rinse following electropolishing and the final rinse following the acid flush. Further B912 prescribes the surface following final rinsing be allowed to thoroughly dry before being placed into service. Passivation vendors will argue that ad
