What is the correct order for the steps in pickling and passivation?

• A. Lines are dried, passivated, rinsed, acidized, degreased, flushed
• B. Lines are rinsed, flushed, dried, passivated
• C. Lines are acidized, rinsed, flushed, degreased, dried, passivated
• D. Lines are flushed, degreased, rinsed, acidized, rinsed, passivated, dried

Answer: (D)

The steps follow a logical surface preparation sequence: purge the line first to remove loose debris, then remove oils or greases, rinse to clear the degreasing agent, apply acid cleaning to remove oxides and scale, rinse to remove the acid, perform the passivation to form the protective oxide film, and finally dry to remove moisture. This order ensures each treatment can work on a clean surface without contamination from previous steps, and that moisture won’t interfere with forming the passive layer. Skipping flushing or degreasing, or drying before passivation, would leave contaminants or moisture that could hinder effective cleaning, oxide removal, or the formation of a stable passive film.