The standard confirms that carbon steel is the primary material for tanks, piping, and fittings for concentrated $H_2SO_4$, provided the acid concentration remains above 90% and velocity is controlled.
NACE RP 0391 requires three levels of inspection: nace rp 0391 pdf
Carbon steel is the most common material for concentrated HF storage and piping. The guide explains the phenomenon of "passivation." The standard confirms that carbon steel is the
One of the most valuable parts of the PDF is the guidance on inspection. It defines how to check for holidays (pinholes), thickness, and adhesion. Because these linings are often applied in thick films, standard inspection methods for thin-film paints may not apply. It defines how to check for holidays (pinholes),
NACE RP0391, titled "Materials for the Handling and Storage of Concentrated Sulfuric Acid at Ambient Temperatures," is a standard practice developed by NACE International (now part of AMPP: Association for Materials Protection and Performance).
The standard specifically addresses the concentration range of 90% to 100% concentrated sulfuric acid at temperatures ranging from 32°F to 120°F (0°C to 49°C) . It does not cover oleum (fuming sulfuric acid) or dilute acids, which behave completely differently.