NACE RP0391 (now officially NACE SP0391 ) is a technical standard titled "Materials for the Handling and Storage of Commercial Concentrated Sulfuric Acid at Ambient Temperatures". It provides critical guidelines for the design and material selection for systems managing 90% to 100% sulfuric acid ( cap H sub 2 cap S cap O sub 4 ANSI Webstore Key Technical Scope Concentration Range : Specifically covers concentrated sulfuric acid between 90% and 100% Temperature Range