Corrosion inhibition assessment for 5xxx series aluminium alloy using droplet evaluation technique
Creators: name: Gamaleldin, Karim
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 340604
subject: Electrochemistry
classificationCode: 400499
subject: Chemical engineering not elsewhere classified
classificationCode: 401699
subject: Materials engineering not elsewhere classified

description: Aluminium alloy 5083 (AA5083) is one of the commonly used metals in marine applications due to its low-density materials, good mechanical properties, and high resistance to corrosion. On the alloy surface under normal atmospheric conditions. The oxide film formed on the aluminium alloy surface is non-uniform, thin and non-coherent. Therefore, it imparts a certain level of protection under normal conditions. When exposed to environments containing halide ions, of which the chloride is the most frequently encountered in service, the oxide film breaks down at specific points leading to the formation of pits on the aluminium surface. This type of corrosion is known as pitting corrosion. 

Traditional techniques used to evaluate corrosion and corrosion inhibitors can be time-consuming. However, high-throughput methodologies can be used to conduct a large number of simultaneous experiments in a shorter period of time than traditional assessment tests. Consequently, there is an urgent need to discover and develop new rapid screening methodologies that can be used as a preliminary screening method prior to supporting traditional electrochemical methods and computational methods to design new inhibitors.

Therefore, the aim of this research project was to develop a new rapid screening method for metals susceptible to pitting corrosion and assess the performance of corrosion inhibitors using a droplet-based technique. The Master's by research project was divided into two parts. A systematic and rapid droplet-based strategy was used in Part 1 to screen a wide range of corrosion inhibitors for AA5083 and different variations in the inhibitors’ molecular structures. Further characterization of the performance and associated mechanisms of inhibition, including any adsorption or film-forming properties, was carried out in Part 2 on selected shortlisted inhibitors.

In Part 1, a series of trials and experiments have been conducted on 21 corrosion inhibitors to figure out the optimal cleaning methods, surface preparation and condition of using optical profilometry to assess droplets of the inhibitors. While in Part 2, a series of methods were used, including electrochemical and surface characterization, to reveal the long-term performance of two promising inhibitors that were selected from the droplets’ study. 

Overall, the thesis successfully establishes several significant findings over the course of this master’s by Research project, developing a high throughput droplet-based technique, revealing its advantages and limitations in the evaluation of pitting corrosion and corrosion inhibitors of AA5083. 

The main outcome of this thesis is providing a new high throughput screening tool that will help the corrosion community in screening new corrosion inhibitors in a rapid and effective way.