For steel sprinkler piping systems corrosion that results in pipe leakage or obstruction is the most significant issue for owners of water-based fire protection sprinkler systems (FPS) in terms of both cost and system reliability. Corrosion damage leading to mechanical failure or water damage significantly adds to the lifecycle cost of sprinkler protection systems in buildings.[1][2][3][4] A nitrogen generator inerting system was used to study the effectiveness of using nitrogen as a supervisory gas to mitigate sprinkler pipe corrosion for both dry and wet type FPS.In dry or preaction systems pipe corrosion is caused primarily by constant replenishment of oxygen from the supervisory compressed air and the trapped water from system commissioning and trip testing that introduces water into the piping.[5] In wet systems severe pipe corrosion/leakage can often be found close to any air gaps in the pipe which provide the oxygen source for steel pipe corrosion.[6]In this paper a compressed nitrogen corrosion test apparatus was designed and constructed which supplied a blanket of pressurized nitrogen within a test pipe array including galvanized steel pipe (dry system) partially filled with tap water and black steel pipe (wet system) fully filled with tap water. For comparison/control purposes the test apparatus also included a (compressed) air test pipe array. Corrosion test coupon assemblies consisted of galvanized steel and carbon steel coupons which were fully immersed in the tap water and removed periodically for corrosion rate calculation based on weight changes over exposure time.The 12 months testing results show that corrosion rates of carbon steel and galvanized steel coupons in simulated dry pipe systems containing trapped water can be reduced with compressed nitrogen. Up to 9 months testing results show that corrosion rates of carbon steel coupons in simulated wet pipe systems can also be reduced with compressed nitrogen.Keywords: Sprinkler Pipe Corrosion Nitrogen Supervisory Gas Corrosion Mitigation Dry Preaction and Wet Fire Protection Sprinkler SystemReferences:[1] Hague D.R. “Water-Based Fire Protection Systems Handbook” 2nd edition NFPA Quincy MA 2008.[2] “Standard for the Inspection Testing and Maintenance of Water-Based Fire Protection Systems” 2011 edition NFPA 25 2011.[3] FM Global Data Sheet 2-0 “Installation Guidelines for Automatic Sprinklers.”[4] FM Global Data Sheet 2-81 “Fire Protection System Inspection Testing and Maintenance and Other Fire Loss Prevention Inspections.”[5] Su P. and Fuller D. “Steel Piping Material Corrosion Dry and Pre-Action Fire Protection Systems” Sprinkler Age February 2013 pp. 22-26.[6] Su P. Tatar F.W. Chivukula S. Doerr W.W. “Weld Seam Corrosion of Steel Sprinkler Pipe” CORROSION 2013 Paper # 2140 NACE International Houston TX 2013.