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The light-weight aluminium alloys play an important role in reducing emissions from the transport industry. However, to take full advantage of these, the corrosion mechanisms that govern their failure need to be properly understood. Hence, the electrochemical response, especially after passive film breakdown, of the aluminium alloy AA5083 was analysed via potentiodynamic polarisation. By starting the scans at the relatively negative potential of −1.4 V (vs. SCE), the reduction of water in the electrolyte causes a localised increase in pH, leading to a preferential attack on the susceptible regions in the (sensitised) microstructure; that is, the deleterious β-Al3Mg2 along the grain boundaries. Subsequently, in the later stages of the potentiodynamic scan, these regions that have been degraded by the dissolution of β-Al3Mg2 undergo imperfect repassivation, leading them to be vulnerable to localised breakdowns. These conditions allowed for the discovery of a discernible trend after breakdown, in which AA5083 microstructures with a more extensive β-Al3Mg2 region (both in size and in amount) recorded a more rapid increase in the measured current density. In particular, the potential at which the anodic current density reached 1 × 10−4 A cm−2 was correlated with the extent of β-Al3Mg2 formed during isothermal heat-treatments. This work provides a possible pathway towards the development of an electrochemical quantification technique for the extent of β-Al3Mg2 growth, degree of sensitisation, and, ultimately, the intergranular corrosion (IGC) susceptibility of the microstructure of AA5083 components used in industrial applications.
Yanhan Liew; Sudesh Wijesinghe; Daniel Blackwood. Investigation of the Electrochemical Breakdown Response in Sensitised AA5083 Aluminium Alloy. Sustainability 2021, 13, 7342 .
AMA StyleYanhan Liew, Sudesh Wijesinghe, Daniel Blackwood. Investigation of the Electrochemical Breakdown Response in Sensitised AA5083 Aluminium Alloy. Sustainability. 2021; 13 (13):7342.
Chicago/Turabian StyleYanhan Liew; Sudesh Wijesinghe; Daniel Blackwood. 2021. "Investigation of the Electrochemical Breakdown Response in Sensitised AA5083 Aluminium Alloy." Sustainability 13, no. 13: 7342.
Corrosion protection coatings need frequent developments to cater to different challenges arising from users. In addition to a long lasting corrosion protection, aesthetic requirements and multi-functional properties by the same coating system are prominent demands to be considered. Productivity is another vital factor to be considered, as there is a thriving demand from users to have more productive coating systems, such as a smaller number of layers in a system. Thus, attention to using different coating technologies is an essential step to fulfil these demands. This work investigates the use of sol-gel technology as a topcoat on a zinc rich primer to form a two-coat system. A colored sol-gel topcoat on a zinc primer was developed as a two-coat system to replace the current three or multi-coat systems to improve productivity while maintaining the sacrificial protective capability. The overall corrosion protection performance together with the color retaining capability was evaluated in this development. As another step forward, the development of sol-gel technology as a topcoat with additional inhibitive corrosion protection was investigated. Two corrosion inhibitors, namely molybdate and cerium(III), were loaded onto suitable inorganic oxide carriers and then incorporated into sol-gel coatings to provide an inhibitive protection other than the barrier protection. The corrosion performance of the coatings was evaluated using electrochemical impedance spectroscopy (EIS). Sol-gel coating with a cerium(III) system attained the highest impedance and proved to be the best candidate. The mechanical and physical properties of the coating systems are tested using international standard methods.
Wenjin Yan; Wee Kit Ong; Linda Yongling Wu; Sudesh L. Wijesinghe. Investigation of Using Sol-Gel Technology for Corrosion Protection Coating Systems Incorporating Colours and Inhibitors. Coatings 2019, 9, 52 .
AMA StyleWenjin Yan, Wee Kit Ong, Linda Yongling Wu, Sudesh L. Wijesinghe. Investigation of Using Sol-Gel Technology for Corrosion Protection Coating Systems Incorporating Colours and Inhibitors. Coatings. 2019; 9 (1):52.
Chicago/Turabian StyleWenjin Yan; Wee Kit Ong; Linda Yongling Wu; Sudesh L. Wijesinghe. 2019. "Investigation of Using Sol-Gel Technology for Corrosion Protection Coating Systems Incorporating Colours and Inhibitors." Coatings 9, no. 1: 52.
A 2-part epoxy-siloxane coating cured with amino silane has been developed to provide corrosion protection on carbon steel (CRSS) using dip-coating to deposit a two layer structure. Amino silane served both as hardener, reacting with the epoxide group to initiate crosslinking, and as coupling agent to enhance adhesion of hybrid polymer resin to the metal surface. Corrosion resistance in different chemical media and mechanical properties of the coating were systematically studied and characterised. It is found that prehydrolysed amino silane can speed up drying of epoxy-siloxane coatings, touch dry coatings are obtained within 1 h. Coating materials employing a mixed solvent of ethanol and methyl ethyl ketone exhibited a longer pot life, and the resultant coatings showed no degradation of their corrosion resistance after one month chemical immersion tests in alkaline, acidic and saline conditions. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion properties of these coatings.
Min Qian; Andrew Mcintosh Soutar; Xiu Hui Tan; Xian Ting Zeng; Sudesh L. Wijesinghe. Two-part epoxy-siloxane hybrid corrosion protection coatings for carbon steel. Thin Solid Films 2009, 517, 5237 -5242.
AMA StyleMin Qian, Andrew Mcintosh Soutar, Xiu Hui Tan, Xian Ting Zeng, Sudesh L. Wijesinghe. Two-part epoxy-siloxane hybrid corrosion protection coatings for carbon steel. Thin Solid Films. 2009; 517 (17):5237-5242.
Chicago/Turabian StyleMin Qian; Andrew Mcintosh Soutar; Xiu Hui Tan; Xian Ting Zeng; Sudesh L. Wijesinghe. 2009. "Two-part epoxy-siloxane hybrid corrosion protection coatings for carbon steel." Thin Solid Films 517, no. 17: 5237-5242.