Investigation of calcareous deposits formation on copper and 316L stainless steel under cathodic polarization in artificial seawater

Abstract

The formation and growth of calcareous deposits on 316L stainless steel and copper under cathodic polarization in artificial seawater were investigated by electrochemical tests and analytical techniques such as SEM, EDX and XRD. The deposits mineral compositions were related to the types of metallic materials and were different on each substrate. On 316L stainless steel at potentials less negative than the water reduction potential (−1100 mV/SCE), the deposits were composed of aragonite with low amounts of brucite; at the potentials more negative than the water reduction potentials, only of brucite. Around the water reduction potentials, the deposits were composed of both aragonite and brucite together. However the formation of brucite was noted before activating the water reduction processes. The results were moderately similar to that on mild steel and the type of deposited phases depended on potentials, at which the cathodic protection was carried out. The deposits formed on copper differed from those on 316L stainless steel and the types of deposited phases were independent from water reduction potential on copper (−1150 mV/SCE). Hence, the deposits were composed only of aragonite at all potential ranges. Due to the low current densities observed in chronoamperometric curves during cathodic polarization and in sufficient alkalinity, it seemed that the brucite could not deposit on this metallic substrate.