Corrosion of Reinforcing Steel In Concrete in Marine Atmospheres

Where a reinforced concrete structure is exposed to a marine atmosphere, serious corrosion of the reinforcing steel sometimes takes place within a relatively short time and the concrete cover round the reinforcing is spalled off. This phenomenon,, examples of which are described, constitutes a major problem in South Africa, particularly in coastal areas. No exhaustive work on this particular subject is described in the literature and because of the nature of concrete, conventional methods of corrosion prevention find little direct application. The reaction proceeds by electro-chemical mechanisms whose emf’s derive from differences in pH, aeration or other factors but whose severity is influenced mainly by presence of sodium chloride in the concrete. Accelerated corrosion tests in a salt spray cabinet using steel reinforced mortar specimens indicated that factors of considerable significance are cover to the steel, protective coatings to the mortar, and the curing, cement content and water cement ratio of the mortar. The effects of these variables in the corrosion of the steel are discussed. A comprehensive series of both accelerated and natural exposures of reinforced concrete specimens in progress is outlined. 6.6.5