  Water solid interfacial reactions are critical to understanding corrosion.
More specifically, it is notoriously difficult to determine how water and solid
interact beyond the initial chemisorption to induce the surface dissolution.
Here, we report atomic-scale mechanisms of the elementary steps during SiC
hydrothermal corrosion, from the initial surface attack to surface dissolution.
We find that hydrogen scission reactions play a vital role in breaking Si-C
bonds, regardless of the surface orientations. Stable silica layer does not
form on the surface, but the newly identified chemical reactions on SiC are
analogous to those observed during the dissolution of silica. SiC is dissolved
directly into the water as soluble silicic acid. The rate of hydrothermal
corrosion determined based on the calculated reaction activation energies is
consistent with available experimental data. Our work sheds new light on
understanding and interpreting the experimental observations and it provides
foundation for design of materials that are resistant to corrosion in water.
