Influence of Temperature and Exposure Time Upon Calcareous Deposits

Experiments have been performed where cylindrical 1018 steel specimens were polarized to –0.900 V (SCE) in natural seawater at 24 and 3 C with rotation speeds of 0 and 0.83 Hz. The nature of the calcareous deposits that formed was characterized first by monitoring current density (CD) during the experiments and secondly by post-test SEM investigation of deposit morphology and thickness and by EEDS analysis of deposit composition. The dependence of cathodic CD and film composition upon temperature and exposure time has been established, and the observed trends have been interpreted in terms of (1) the temperature dependence of the solubility limit and the relative nucleation and growth rates for calcium- and magnesium-rich phases and (2) possible electrical conductive behavior of magnesium-rich deposits.