Mechanisms for the Atmospheric Corrosion of Carbonate Stone

The physical and chemical phenomena responsible for the atmospheric corrosion of carbonate stone are presented. Corrosion product formation, morphology, and chemical makeup are discussed in the context of calcium‐containing minerals and other crystalline structures that thermodynamics and kinetics suggest are likely to be present. Formation pathways for the minerals most often reported to occur in carbonate corrosion layers are shown in schematic diagrams. The dominant corrosion products are sulfates and oxalates, the former resulting from interactions with atmospheric sulfur dioxide or sulfate ions, the latter from oxalate secretions from the biological organisms present (and perhaps to some extent from oxalate deposited from the atmosphere). The degradation processes are enhanced by the catalytic action of transition metal ions present in the stone and of soot deposited from the atmosphere.