In a marine environment, what is one effect of high chloride content on corrosion?

• A. It tends to accelerate corrosion of steel by promoting localized attack
• B. It prevents corrosion by passivation
• C. It has no effect on corrosion
• D. It only affects aluminum, not steel

Answer: (B)

Chloride ions in seawater are especially aggressive toward metals because they break down protective oxide films and concentrate at flaws, which initiates pits. In steels, there isn’t a stable passive film to begin with, and even where a passive layer forms on some alloys, chloride ions disrupt it, leading to localized attack rather than uniform protection. So high chloride content does not prevent corrosion; it accelerates it by promoting pit formation and other localized corrosion modes. The idea that chloride prevents corrosion by passivation isn’t accurate, since chloride undermines passivation and makes corrosion more likely, not less.