TABLE OF CONTENTS Dissolved substances in water have an important effect on both corrosion and corrosion control. This section provides a brief overview to point out some of the most important factors.
Table 17.3 lists some of the chemical factors that have been shown to have an important effect on corrosion or corrosion control. Several of these factors are closely related, and a change in one changes another. The most important example of this is the relationship among pH, carbon dioxide (CO 2), DIC concentration, and alkalinity. Although CO 2 is frequently considered to be a factor in corrosion, there is no clear evidence that direct corrosion reactions include CO 2 as a reactant (Singley et al., 1984; AWWA, 1986). In some cases, the rate of CO 2 hydration might influence the bicarbonate concentration, and, hence, the buffering ability of the water, but the important corrosion effect usually results from pH and complexation by bicarbonate or carbonate ions. The dissolved CO 2 concentration is interrelated with pH and DIC concentration. Knowing all of the complex equations for these calculations is not necessary, but knowing that each of these factors plays some role in corrosion is useful.
| Factor | Effect |
|---|---|
| pH | Low pH may increase corrosion rate and the strength of oxidizing agents; high pH may protect pipes by favoring effective passivation films and decrease corrosion rates; possibly causes or enhances dezincification of... |
