Protons from hydrogen or water vapour may dissolve in oxides and other
corrosion products, and may affect, and in some cases, dominate their
defect structures. Defect-dependent properties like scale growth and
plastic deformation them become dependent on the ambient hydrogen or w
ater vapour pressure. Small concentrations of protons may enhance the
transport of oxygen in the form of hydroxide ion diffusion. Furthermor
e, the transport of protons through a scale (dissolving as hydrogen in
the metal), can replace the outward transport of electrons during sca
le growth. Recent literature results indicate that protons can be domi
nant defects in Y2O3, Al2O3 and Cr2O3 under certain conditions.