TABLE OF CONTENTS Metal species can be released into water either from the simple dissolution of existing scale materials, or actual electrochemical corrosion followed by dissolution. In some cases, scale materials formed from corrosion by-products may be eroded from the pipe surfaces. Almost all mineral salts dissolve in water to some extent, from insignificant traces to high concentrations in seawater. This section will provide a general overview of some aspects of the electrochemistry of metallic corrosion as it applies in the context of drinking water treatment. However, many specialized texts on electrochemistry and electrochemical corrosion are available (Piron, 1991; Ailor, 1970; Bockris and Reddy, 1973; Butler and Ison, 1966; NACE, 1984; Pourbaix, 1966, 1973; Thompson, 1970) and should be consulted by readers who are interested in a comprehensive examination of the subject.
For corrosion of any type to occur, all of the components of an electrochemical cell must be present. These include an anode, a cathode, a connection between the anode and cathode for electron transport, and an electrolyte solution that will conduct ions between the anode and cathode. The anode and cathode are sites on the metal that have different electrical potential. Differences in potential may arise because metals are not completely homogeneous. If any one of these components is absent, a corrosion cell does not exist and corrosion will not occur.
Oxidation and dissolution of the metal takes place at the anode. The electrons generated by the anodic reaction migrate to...
