I am specifying pipes for a water system with 500 ppm chloride in solution. Ordinarily we would specify 316L stainless steel to limit the corrosion, but I was asked if we could instead specify carbon steel pipe with a corrosion allowance. So instead of the typical schedule 40 pipe, could I realistically use schedule 80 or 120 etc?
My gut reaction is that you will never really even have a "protective" oxide layer with water continually flowing, so you will just continually corrode the pipes out. All that will be gained with thicker pipe is that it will last longer before failure, but you will have increased corrosion products to remove from the flow stream over time. I could not really find any good resources talking about chloride effects on carbon steel pipe since the general consensus is that stainless should be used for this application.