How deep should concrete cover be over rebar?

The 'cover depth' is critical for protecting steel rebar from carbonation and chloride attack. British Standards (BS 8500) typically recommend a minimum cover of 25mm to 50mm, depending on exposure conditions (e.g., marine environments require deeper cover). If the cover is too shallow, environmental agents reach the steel quickly, causing premature corrosion. In repairs, if we cannot achieve the original cover depth, we use specialized coatings or extra-dense repair mortars to provide equivalent protection.