Steven Michael Ford, do hereby declare that this thesis is my own unaided work. This thesis has not been submitted in part or in full at this or any other university. This report is submitted in fulfilment of the degree of Master of Science in Engineering at the University of the Witwatersrand. / Aluminium, although often possessing adequate strength and toughness for a specific application, may be deemed unsuitable due to a less than satisfactory corrosion resistance. This unacceptable behaviour is especially prominent in the local mining industry where aluminium alloys corrode severely in the high chloride and sulphate containing waters. Of notable importance and the major motivating force for this research was the historically poor perfomance of aluminium alloy mine cages, which are suited to the task excepting for their unsatisfactory corrosion resistance. Of general importance however, is that the mining sector in South Africa represents a sizeable portion of the economy and could thus become a much greater consumer of aluminium if the metal's corrosion resistance could be improving Apart from varying the composition of the alloy, the other basic technique of increasing a metal's resistance to an environment is by applying a coating of some sort. This research looks into the use of aluminium-based metal sprayed coatings as a form of protection for various aluminium and steel substrate alloys. The purpose of a metal sprayed layer is not merely to isolate the substrate from the environment, hut also to act as a sacrificial anode at regions where the substrate is exposed. Previous work suggested that alloys of aluminium/zinc/indium produced excellent sacrificial anodes and were thus selected for this research. The zinc and indium were always alloyed with pure aluminium, with the percentage zinc varying between 0 and 12%. All the coating alloys were sprayed on a AA6261 and AA5083 aluminium alloys, a metal matrix composite and a mild steel alloy, Various electrochemical and immersion trials were then carried out in several synthetic mine waters and other corrosive media. The basic conclusion to be drawn from the results achieved is that the optimum coating for a particular substrate alloy is the one that provides the greatest potential difference between it and the substrate, while still lasting the required lifetime of the component. The reason for this is that the greater the potential difference, the better the sacrificial protection and hence the better the protection offered to any exposed areas on the surface. The fact that the coating corrodes away with time means that a balance must be found between sacrificial behaviour and required lifetime. / Andrew Chakane 2018

Indiana University-Purdue University Indianapolis (IUPUI) / This work is focused on developing viable self-healing coatings, especially considering the viability of the coating in a commercial context. With this in mind, finding low cost healing agents, with satisfactory healing and mechanical properties as well as adapting the healing system for use in coatings was required. Seven potential healing agents were evaluated and an air-drying triglyceride (linseed oil) was identified as the candidate healing agent. Different encapsulation techniques were evaluated and ureaformaldehyde microcapsules were chosen as the candidate encapsulation technique. Self-healing coatings were fabricated using urea-formaldehyde encapsulated linseed oil. EIS, SEM and TGA technologies were used to evaluate mechanical performance, corrosion resistance, and self-healing performance.