Runoff zinc corrosion film

The zinc losses for longer exposures. Figure 6, show a decidedly different result. Here there is an increasing trend of zinc loss from the corrosion film as the hydrogen ion load increases. A least squares fit of the data yields the following relationship between the zinc runoff loss, Zn/dm ), and the hydrogen ion... 

Runoff Losses Due to Hydrogen Ion Loading. Runoff losses from zinc, and presumably galvanized steel, are dependent upon hydrogen ion load in 3- and 12-month exposure. Such an effect is not apparent in 1-month exposures. Hydrogen ion dissolves zinc carbonate, perhaps the major constituent of the corrosion film, by the reaction... 

Additional corrosion film is lost in the runoff due to the limited solubility of the corrosion product in rain. The relative contribution of these effects to the runoff in 3- and 12-raonth exposures was 55 pet dissolution and 45 pet hydrogen ion loading. To maintain the stable corrosion film that develops on zinc in long-term exposures, it is evident that zinc must corrode at a rate sufficient to replace the corrosion product lost in runoff. 

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