Brian Dalder Forum Moderator 169 Posts
Re: What material would work best for 98% Sulfuric acid transfer piping/fittings?8 April 2011 at 1:29pm
The corrosivity of sulfuric acid depends on many factors including temperature, concentration, the presence of oxidizing or reducing impurities, velocity effects, and solids in suspension.
For 90% to 100% sulfuric acid, a good choice would be 316L stainless steel. Since it is a molybdenum bearing grade, it has improved resistance to velocity enhanced corrosion or impingement in valves. For welded piping, the low carbon of 316L stainless steel prevents intergranular corrosion if dilution or contamination occurs.
If plastics are preferred, the following fluorinated plastics are resistant to concentrated acids at ambient temperature: polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), ethylene chlorotrifluoroethylene (ECTFE), fluorinated ethylene propylene (FEP), and ethylene trifluoroethylene (ETFE). Because of the mechanical weakness of thermoplastics, lined piping should be considered. The chemical resistance of thermoplastic materials using plasticizers should always be verified with the manufacturer. Polyethylene (PE) and polypropylene (PP) are subject to environmental cracking, the likelihood of which increases with increasing concentration and temperature. Careful review of the long-term performance of these materials should be performed prior to use.
For additional information, consult NACE Recommended Practice RP-0391 "Materials for the Handling and Storage of Commercial Concentrated (90 to 100%) Sulfuric Acid at Ambient Temperatures."