Recently, interest in long-term underground corrosion has greatly increased because of the ongoing need
to dispose of nuclear waste. Additionally, the Nuclear Waste Policy Act of 1982 requires disposal of high-level
nuclear waste in an underground repository. Current contaminant release and transport models use limited
available short-term underground corrosion rates when considering container and waste form degradation.
Consequently, the resulting models oversimplify the complex mechanisms of underground metal corrosion. The
complexity of stainless steel corrosion mechanisms and the processes by which corrosion products migrate from
their source are not well depicted by a corrosion rate based on general attack. The research presented here is the
analysis of austenitic stainless steels after 33½ years of burial. In this research, the corrosion specimens were
analyzed using applicable ASTM standards as well as microscopic and X-ray examination to determine the
mechanisms of underground stainless steel corrosion. As presented, the differences in the corrosion mechanisms
vary with the type of stainless steel and the treatment of the samples. The uniqueness of the long sampling time
allows for further understanding of the actual stainless steel corrosion mechanisms, and when applied back into
predictive models, will assist in reduction of the uncertainty in parameters for predicting long-term fate and
transport.
Keywords: stainless steel, underground corrosion