Corrosion Protection and Corrosion Protection of Building Materials by Carbonation

Section: Articles
Keywords: surface coating, surface filler, protective barrier, building materials, chemical bonding parameters, carbon dioxide, carbonic acid

Carbon dioxide interacts with building materials, producing a corroding effect. It enters inside materials by diffusion or osmosis process, and in the presence of moisture, it produces H₂CO₃, which decreases the pH value and accelerates chemical and electrochemical reactions with building materials. The carbonation reaction produces deterioration inside and outside of building materials. Destructive attacks are developed by CO₂ in concrete, which is the main cause of its corrosion. Chemical reactions occur with concrete and mortar in the presence of water. CO₂ reacts with Ca(OH)₂ and Mg(OH)₂ to form the voluminous compound CaCO3.MgCO3.H2O. This compound increases the size of building components; thus, cracks develop. It also generates swelling and dissolving effects in building materials. H₂CO₃ creates an acidic environment for reinforced iron bars in concrete and forms a corrosion cell with an iron bar; thus, corrosion starts, and disbanding occurs between set cement and iron bars. In this way, concrete is detached with an iron bar. Metallic bar exhibits galvanic, pitting, crevice, and stress corrosion. CO₂ environment corrosion of building materials is controlled by the coating of octahydrodibenzo(a,d) (Singh, 2015a)annulene-5,12-diphenyhydrazone and CoS filler. These compounds are developed as composite barriers on the interface of building materials to stop diffusion or osmosis of CO₂, which works as an anticarbonation coating. The corrosion rate of building materials was determined by gravimetric and potentiostat techniques. Octahydrodibenzo(a,d) (Singh, 2015a)annulene-5,12-diphenyhydrazone was synthesized and used as an anticarbonation coating. The composite layer formation was studied by thermal parameters like activation energy, heat of adsorption, free energy, enthalpy and entropy. The surface coverage area and coating efficiencies results indicate that the coating and filler compounds provide an anticorrosive composite barrier.