Insight into atmospheric pitting corrosion of carbon steel via a dual-beam FIB/SEM system associated with high-resolution TEM

Abstract Carbon steel experiences serious pitting corrosion in the atmospheres containing chloride ions. The present research is focused on revealing a three-dimensional chemical and microstructural insight into pitting corrosion with high spatial resolution nano-tomography by addressing 1018 carbon steel after exposed in the marine atmosphere. A well-defined core-shell structure for pitting corrosion products was revealed by using a combination of dual-beam focused ion beam system with scanning electron microscope (FIB/SEM) and high-resolution transmission electron microscope (HRTEM). The core is made of ferric chloride and the shell is constituted with iron oxides. Pitting corrosion is a self-catalytic process and the corrosion products grow to be porous flower-type structures. The porosity in the core provides a diffusion path for the ions. Inclusions promote pitting corrosion growth.