Environmental Engineering Reference
In-Depth Information
Figure 2.25
Passivation of titanium by galvanic coupling with platinum air-free acid
solution.
Figure 2.26
Effect of galvanic coupling with platinum on corrosion behavior of an
iron in air-free acid solution.
2.4.3 Theories of Passivity
There are two distinct theories of passivity: oxide film theory and adsorption
theory.
The oxide film theory [3] holds that the passive film is a diffusion barrier
layer of reaction products, often an oxide, which separates the metal from the
environment. Many metals resist further corrosion with the buildup of an initial
corrosion product film, e.g., lead sulfate film on lead immersed in sulfuric acid.
