Aqueous layer corrosion-stimulating gases

In outdoor exposure conditions subject to wet-dry cycles, the actual concentration of most corrosion-stimulating gases under many conditions is not at equilibrium between the gas in the atmosphere and the same gas in the aqueous layer. Even so, thermodynamic considerations have been used for predicting the formation of different corrosion end-products and their stability. Figure 3.1 is a schematic illustration of processes occurring at the aqueous layer. 

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