Which environmental factors accelerate reinforcement corrosion?

• A. High moisture with low chloride exposure.
• B. Chloride exposure (deicing salts, seawater), high moisture, and carbonation.
• C. Low humidity and dry storage.
• D. Exposure to ozone only.

Answer: (B)

In reinforced concrete, corrosion of the steel gets started when moisture allows ions to move and react at the steel surface. The most aggressive combination is presence of chlorides (from deicing salts or seawater), high moisture to carry those ions, and carbonation that lowers the concrete’s pH. Chlorides bypass the protective, high-pH, passive film on the steel, initiating corrosion even if moisture is not extreme. Moisture provides the electrolyte path for the electrochemical reactions, so plenty of it speeds things up. Carbonation reduces the pore solution’s alkalinity, weakening or removing that protective passive layer, making the steel susceptible to corrosion when chlorides and moisture are present. Together, these factors create the fastest, most extensive reinforcement corrosion. Dry conditions or exposure to ozone alone don’t provide the necessary electrolyte environment or depassivation mechanism, so they don’t accelerate corrosion as effectively.