A study of localised corrosion within occluded cells on a simulated cast iron artefact in chloride solution

摘要

The chemical behaviour within the occluded cell of simulated cast iron artefact in 3.5 percent NaCl solution has been investigated by means of a simulated occluded cell. It was observed that the pH value and the amount of Cl{sup}- migration in the occluded cell were related to the quantity of passing electric current. Electrochemical techniques were capable of providing information on the behaviour of the cast iron in a simulated occluded cell at various time intervals. The results of potentiodynamic polarisation and impedance measurements indicated that corrosion potentials became more negative and the cast iron was corroded more seriously. SEM micrographs clearly revealed the morphologies of specimens after simulated occluded cell galvanostatic tests for different time intervals at 1 mA/cm{sup}2 anodic current density. An auto-catalysing process was responsible for the enrichment of chloride ions in occluded cell which was confirmed by Energy Dispersive Spectroscopy (EDS).