Calcareous deposit precipitation on cathodically polarized carbon steel in seawater exposed to natural daylight cycles

This paper deals with calcareous deposit precipitation occurring on cathodically protected carbon steel in natural seawater. Daylight cycles related effects were here investigated. Being O2 both cathodic reactant and key molecule of aerobic environments, a potential involving oxygen limiting current without hydrogen evolution (-850 mV vs. Ag/AgCl) was employed. Comparison of natural seawater with NaCl 3.5% wt. solution data showed that sunlight radiation plays a primary role with respect to temperature in affecting cathodic currents even in presence of electro-accreted aragonite. Calcareous deposit morphology and composition was investigated through SEM, highlighting properties and peculiarities.