Reinforced concrete near the coast can be exposed to chlorides from marine environments. Where chlorides reach reinforcing steel in sufficient concentration, corrosion risk can increase.
Chloride exposure
Salt laden environments can contribute to corrosion risk, particularly where concrete cover, cracking or permeability allows contaminants to reach the reinforcement.
Carbonation
Carbonation can also reduce the alkalinity that normally protects embedded steel. It is a different mechanism from chloride attack but can lead to the same corrosion problem.
Site specific assessment
Distance from the ocean alone does not diagnose concrete cancer. Building age, material quality, cover, moisture and maintenance history all matter.
What to do next
Take clear photos of the wider area and close up damage, note the property location and where the concrete is situated, then arrange an on site assessment so the repair scope can be priced accurately.