Most metals will corrode within a certain range of electrical solution potential and solution pH. At potentials more negative than this range, corrosion ceases (cathodic protection). At potentials more positive than this range, several metals become passive. For these metals the potential can be shifted electropositively into the passive range through anodic protection (AP). AP is especially applicable to sulfuric acid (H2S04) and caustic liquor environments. It often permits a designer to use a low alloy rather than a corrosion-resistant metal, at an overall cost saving.
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