In all piping systems, the expected corrosion rate may be constant or change with time. External corrosion (atmospheric corrosion, dampness in the soil, or chlorides from insulation) may be a factor. Many companies usually specify a 1/16-inch (0.0625") minimum corrosion allowance for carbon steel and low alloy steel piping if the corrosion rate can be predicted accurately and is less than a defined threshold (3 mils per year or less as an example). For stainless steel, a 1/32-inch (0.0 3125") minimum corrosion allowance is usually sufficient.
Corrosion Allowance Standards
- ASME Standards
- ASME B31G - Manual for Determining the Remaining Strength of Corroded Pipelines