Corrosion is a random pitting of the pipe wall, not a uniform boring of the inner diameter. As such, corrosion is a random event. Historically the piping codes have ignored the weight loss due to corrosion, in recognition of the previous statements. Instead, the piping codes only consider corrosion in the final stress calculation.

A model will produce the same results for displacements, reactions, and element forces with or without corrosion specified. The difference between the two (corrosion) situations will be in the stress results.