A model to estimate moisture distribution in porous oxides as a function of atmospheric conditions

• Computation of connected moisture retention and its distribution in porous layers.
• The local and global levels of connected moisture are calculated.
• An extension of Hoshen–Kopelman’s Monte Carlo simulation algorithm is used.
• Dependence of wetness in porous over-layers on relative humidity and temperature.
• A percolation threshold is identified in the percolation parameter P.

An approach is presented for estimating the retention of moisture and its distribution within porous bodies or layers. Corrosion will only occur if moisture above the oxide layer can be connected to the metal/oxide surface. Such local levels of connected moisture and global levels of connected moisture were computed using Monte Carlo simulation as a function of depth in the porous body for several values of percolation parameter P which in turn depends on relative humidity (RH) and temperature (T). The time that an oxide on a metal surface holds connected moisture paths is compared to times that a smooth surface will retain moisture films. The implications for corrosion are discussed.