Page "Galvanization" Paragraph 11

As noted previously, both mechanisms are often at work in practical applications.

For example, the traditional measure of a coating's effectiveness is resistance to a salt spray.

Thin coatings cannot remain intact indefinitely when subject to surface abrasion, and the galvanic protection offered by zinc can be sharply contrasted to more noble metals.

As an example, a scratched or incomplete coating of chromium actually exacerbates corrosion of the underlying steel, since it is less electrochemically active than the substrate.