Oxygen diffusion through paint films

Water and oxygen diffuse through paint film at a relatively high rate. The protective ability of a paint-phosphate film is influenced by the properties of the phosphate film because the film is in contact with the diffused water and oxygen. Film properties of concern are solubility, uniformity, and porosity. 

Table 14.4 Diffusion of oxygen through paint films of thickness 0-1 mm...

Kittelberger and Elm measured the rate of diffusion of sodium chloride through a number of paint films. Calculations based on their results showed clearly that the rate of diffusion of ions was very much smaller than the rate of diffusion of either water or oxygen. Furthermore, they found that there was a linear relationship between the rate of diffusion and the reciprocal of the resistance of the film. This relationship suggests that the sodium chloride diffused through the membrane as ions and not as ion pairs, since the diffusion through the film of un-ionised material would not affect the resistance, because if a current is to flow, either ions of similar charge... 

The diffusion of oxygen through polymer films has been examined by a number of workers. Guruviah measured the permeability to oxygen of films cast from five paints (Tabic 14.4) and compared the results with the... 

---