You can refer following articles regarding corrosion of reinforcement to find your answer: How to Control Corrosion of Steel Reinforcement in Concrete? Protection of Reinforcement Against Corrosion
How to Make Reinforcement Bars Corrosion Resistant? How can the reinforcement bars be made corrosion resistant to be used for reinforced concrete construction?
How to Make Reinforcement Bars Corrosion Resistant?
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Three methods are common to protect reinforcement from corrosion: The most common and most durable method is epoxy coating. This method is extensively used in highway construction, particularly in regions where salts are used for de-icing. Galvanized reinforcement is also available but is much less common, and far less durable. For low-risk applications, reinforcement is usually protected by maintaining adequate concrete cover. Small covers work well for interior dry uses while larger covers are required for concrete continuously in contact with (pH neutral and non-saline) water (eg groundwater).
CORROSION refers to an electrochemical reaction between a metal and its environment. Steel will readily rust unless it is coated. Corrosion occurs when steel reacts with chloride ions (Cl-), CO2 in the presence of a toxic environment. Thus, corrosion is uneven erosion/pitting of metal surface due to intense rusting and is also harmful to the service performance of rebar. There are many ways of reducing the risk of corrosion-related distress in concrete. The first defencing layer is concrete, which should be thick and dense. Also, the cracks should be minimized. The concrete cover should be used appropriately. An additional measure for corrosion-resistant is that corrosion inhibiting admixtures should be used. Epoxy coatings should be done on rebar, which acts as a physical barrier and also isolates the steel from oxygen, moisture, and chloride ions (which are the three primary elements needed for corrosion to occur).