We are a Fire Protection Contractor located in Michigan. We are currently installing an Automatic Fire Protection System within a newspaper printing plant where Class 250 cast iron fitings (steam fittings) were specified. The Class 125 cast iron fitting is the norm for our industry and this specification was interpreted to be a misprint. After a long battle with the engineer we are going to be able to leave the Class 125 fittings in lieu of the 250's, but we have to provide a credit and a 10 year warrenty against corrosion of those fittings. Where do I find information related to corrosion of cast iron materials? All of the fittings in question are manufactured by Ward. The claim by the engineer is that the thicker fitting will last longer and that is why Class 250 was specified. I am not doubting this, but how much longer? It seems to me that the sch. 40 pipe will be rusted far before any cast material. Example of thicknesses in question: 2" Class 125 fitting: .22, 2" Class 250 fitting: .39. This is a standard water based system in a climate controlled building (so excessive het is not the issue). Any info will help, Thank You, Todd Harroun Harroun Fire Protection todd@blharroun.com