Bromide induced corrosion of stainless steels and Ni-based alloys
File(s)
Author(s)
Skountzos, Epameinondas
Type
Thesis
Abstract
Stainless steels and Ni-based alloys are commonly used in the industry due to their mechanical strength and increased corrosion resistance. However, they are not impervious to localised attack in aggressive environments containing halides (F, Cl, Br and I). Significant research has addressed the case of Cl-; however, the mechanism behind Br-induced corrosion is relatively poorly understood. Additionally, the presence of organic acids, such as acetic acid, strongly affects the corrosion behaviour of corrosion resistant alloys (CRAs). Successful corrosion mitigation and appropriate material selection are highly important in process design and require a detailed knowledge of the mechanisms and kinetics of corrosion.
In this work, a combination of techniques probed the mechanism of Br-induced corrosion of stainless steels, assessing the role of acetic acid (HAc) and temperature on pitting corrosion susceptibility. The electrochemical behaviour of stainless steels was studied using planar and one-dimensional artificial pit electrodes, to obtain information on corrosion kinetics and the threshold conditions that sustain stable pit propagation. The effect of pit geometry on one-dimensional mass transport and pit stability was also investigated by finite element modelling of the artificial pit electrode process. In addition, the pitting phenomenology was observed with immersion studies complimented by ex situ characterisation.
It was found that the introduction of HAc increases the likelihood of pitting corrosion, in both SS304 and SS316L. Additionally, the presence of HAc strongly affects the repassivation process in steels, indicating that in high concentrations of both FeCl3 and FeBr3, repassivation is inhibited...
In this work, a combination of techniques probed the mechanism of Br-induced corrosion of stainless steels, assessing the role of acetic acid (HAc) and temperature on pitting corrosion susceptibility. The electrochemical behaviour of stainless steels was studied using planar and one-dimensional artificial pit electrodes, to obtain information on corrosion kinetics and the threshold conditions that sustain stable pit propagation. The effect of pit geometry on one-dimensional mass transport and pit stability was also investigated by finite element modelling of the artificial pit electrode process. In addition, the pitting phenomenology was observed with immersion studies complimented by ex situ characterisation.
It was found that the introduction of HAc increases the likelihood of pitting corrosion, in both SS304 and SS316L. Additionally, the presence of HAc strongly affects the repassivation process in steels, indicating that in high concentrations of both FeCl3 and FeBr3, repassivation is inhibited...
Version
Open Access
Date Issued
2022-04-29
Date Awarded
01/11/2022
Advisor
Ryan, Mary
Sponsor
Engineering and Physical Sciences Research Council
bp-ICAM
Grant Number
EP/L015277/1
Publisher Department
Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)