What factors most influence the rate of steel corrosion in marine environments?

• A. Presence of chlorides and moisture
• B. Absence of oxygen
• C. Dry, inert air
• D. High temperatures alone

Answer: (A)

Corrosion in the sea happens mainly through electrochemical reactions that need a conductive liquid and ions to carry charge. Chloride ions from seawater are especially damaging because they break down the protective oxide film on steel and promote pit formation, leading to much faster, localized corrosion. Moisture provides the electrolyte that allows the anodic and cathodic reactions to proceed on the steel surface, so when seawater is present, the corrosion rate shoots up. Without moisture or with dry inert air, those electrochemical processes are severely reduced, so corrosion is minimal. Temperature can speed things up, but it cannot cause the same rapid deterioration by itself without the moisture and chlorides present. So the presence of chlorides and moisture is what most influences the rate.