Pitting Corrosion of Steel Induced by Al2O3 Inclusions

Abstract

Abstract:To study the effect of Al 2 O 3 inclusions on pitting corrosion in steel, our researchers utilized industrial pure iron as the raw material with the addition of a proper amount of pure aluminum powder to form Al 2 O 3 inclusions. Corrosion experiments were performed by exposing the samples to a 6% FeCl 3 solution at room temperature (25 • C) for different lengths of time. Microscopic corrosion morphology was observed by scanning electron microscope (SEM), and the size change of the inclusions was quantitatively analyzed with Image Pro Plus. The experimental results showed that pitting corrosion arose preferentially around the Al 2 O 3 inclusions, and that pitting corrosion initiated at the junction of the Al 2 O 3 inclusions. The steel matrix dissolved and micro-cracks occurred as the Al 2 O 3 inclusions that were buried shallowly below the surface of the steel matrix promoted corrosion of the steel matrix. As corrosion progressed, the shallowly buried Al 2 O 3 inclusions began to appear on the surface, and the small, shallow inclusions fell off and formed micro pits. Furthermore, the clustered distribution of alumina inclusions had a greater effect on pitting initiation than the alumina inclusions distributed alone.

Mechanism Understanding of the Role of Rare Earth Inclusions in the Initial Marine Corrosion Process of Microalloyed Steels

“…Subsequently, the corrosion behaviors of inclusions in different deoxidized steels were characterized. For most cases, two or more components coexisted in one inclusion, which has been reported in previous studies [37,53,54,55]. As seen in Figure 6, the light part in Al deoxidized steel is denoted as metal oxygen sulfides and/or metal sulfides, M-O x S y (M-S x ), while, the dark part is metal oxides, M-O x , which could be verified by the EDS results.…”

Inconsistent evolvement of micro-structures and corrosion behaviors in cold/warm deformed austenitic stainless steel

“…Inclusions in SS lead to the depletion of Cr in the surrounding materials, which caused the pitting corrosion to be more easily initiated at the inclusions [26]. Generally, inclusions are easy to form at the grain boundary of stainless steel, which are seriously sensitive to corrosion [27]. However, the inclusions will dissolve after pitting corrosion [28], and it was not easy to observe whether the pitting corrosion occurs at the position of the inclusions.…”

Blade Lock Ring of 4th Stage Compressor Rotor: Failure Investigation

“…It is also reported by Liu et al that the pitting corrosion occurs preferentially around the Al2O3 inclusions. As Al2O3 inclusions are stable and hard, during the process of corrosion, these inclusions do not dissolve like MnS [15]. Therefore, pitting corrosion is induced at the interface of the inclusions and the steel matrix and then results in micro cracks.…”