The behaviour of iron electrode in CO2? saturated neutral electrolyte—II. Radiotracer study and corrosion considerations

The radiotracer method described previously was applied for investigations of adsorption processes occuring in the system: iron electrodeposited electrode and CO₂-saturated (¹⁴C-labelled) neutral electrolyte. In addition to adsorption of ¹⁴C-containing species in the electrodeposited film, both reversible and irreversible adsorption of those species was identified. The irreversible adsorption was interpreted to result from incorporation of ¹⁴C-species (most probably HCO^?₃ ions) to the passive layer formed on the iron electrode. The reversible adsorption was concluded to occur due to the weak interactions of carbonic acid with the oxidized iron surface. Lewis acid and base concept of adsorption was used to account for the results. The role of the reversible adsorption process in the accelerated corrosion of steel due to the presence of carbon dioxide in aqueous solutions is discussed.