Mechanistic understanding of aluminium alloy 6063 corrosion in product store enviroments

The PhD thesis investigates the corrosion mechanisms of AA6063 when exposed to chloride bearing droplet deposits. The investigations were carried out using XCT to examine changes in corrosion morphology and the atmospheric corrosion behaviour of AA6063. The effect of parameters such as temperature, oxygen deprivation and humidity are investigated. The study provides a detailed overview of the mechanisms at play when AA6063 is exposed to FeCl3. It also provides an insight into the effects of pH and chloride concentrations in these corrosion reactions. The corrosion behaviour of AA6063 when exposed to FeCl3 droplets is rather surprising as it suffers from more corrosion at room temperature than at 50 °C. This behaviour is observed at different exposure concentrations and also after two exposure periods. The volumes of corrosion products in such environments are shown to be double that at higher temperatures. Oxygen is shown to play a key role in the inhibition of corrosion reactions when aluminium is exposed to FeCl3. Experiments show that the deprivation of oxygen results in the acceleration of corrosion reactions. Interestingly, in conditions where reactions are deprived of oxygen the concentration of FeCl3 is shown to play an increased role in the corrosion reaction. Moisture plays a key role in these corrosion reactions and therefore its influence is investigated. This is done by investigating the effect of multiple wetting periods on the corrosion of aluminium. Experiments demonstrate the significance multiple wetting periods and droplet frequency have in accelerating corrosion reactions. Corrosion experiments investigate using XCT the corrosion rates of AA6063 over a two-year period without the removal of the corrosion products formed on the surface. When corrosion reactions come to completion, experiments show that the corrosion products that remain on the aluminium surface are shown not to further corrode the aluminium. Iron rich deposits on the aluminium surface are shown not to prevent or hinder further corrosion attacks when exposed to additional FeCl3 droplets.