What is the effect of high chloride ion concentration on stainless steel?

High chloride ion concentration significantly impacts the corrosion behavior of stainless steel, particularly by promoting localized corrosion mechanisms such as pitting. Chloride ions are known to disrupt the passive oxide layer that forms on the surface of stainless steel. This passive layer is crucial for protecting the metal from corrosion.

When the chloride concentration increases, the stability of this protective oxide layer can be compromised. The chloride ions penetrate the passive layer, leading to localized attacks, which manifest as small pits. Unlike general corrosion that affects the entire surface area uniformly, pitting corrosion can lead to severe metal loss in small, concentrated areas, potentially resulting in a structural failure if not monitored and addressed.

In contrast, the other options incorrectly suggest that high chloride concentrations either have no effect on corrosion rates, reduce overall corrosion rates, or enhance the protective oxide layer. These statements do not reflect the well-documented effects of chlorides, which are widely recognized in materials science and corrosion engineering literature.