We are designing a sulfuric acid piping system from ships (wharf) to a fertilizer industry; this piping will be about 4 km long and 10 inches-diameter; sulfuric acid is 94-96% concentrated at 45 °C. Which is the most indicated material for the piping: 316L, 304 or 904?
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Brian Dalder Forum Moderator 180 Posts
Re: What's the best material for a sulfuric acid piping system?13 July 2011 at 1:29pmThe corrosivity of sulfuric acid depends on many factors including temperature, concentration, the presence of oxidizing or reducing impurities, velocity effects, and solids in suspension. According to the MTI publication "Materials Selector for Hazardous Chemicals, Vol. 1: Sulfuric Acid, 2nd Edition", neither 304 or 316L (alone) are recommended for concentrated sulfuric acid at 45 °C. For concentrated acid (93% or >) at 40 to 60 °C and pipe diameters > 3 inches, the recommended materials are 304L with anodic protection (AP), 14% silicon-iron, Alloy B-2, Alloy C-276, glass, PVDF or PTFE lined pipe, and high-silicon stainless steel. AP is a technique used to control the corrosion of a metal surface by making it the anode of an electrochemical cell and controlling the electrode potential in a zone where the metal is passive. According to the same MTI publication, practically indefinite equipment life can be achieved with AP, even in hot sulfuric acid, for strongly passivating alloys like 304, 316, and 904L.