Investigation of the influence of sol-gel coating composition on the corrosion protection of aluminium alloy

• Main Author: Tan, Gareth Tze Yuen.
• Other Authors: Chen Zhong
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Materials::Metallic materials::Corrosion
• Online Access: http://hdl.handle.net/10356/15450
• Institution: Nanyang Technological University

Silica and organosilane based coatings were prepared by sol-gel process under the presence of acid catalyst. The coating compositions were varied by introducing different levels of impurities in the form of salts to investigate their effect on corrosion protection provided by the coating and thus to determine the coating's tolerance for impurities that may be present in lower grade starting materials. The coatings were deposited on 6061 T6 aluminium alloys by dipping. The surface morphology of the films was characterized using optical microscopy. Corrosion protective values of coatings were evaluated by potentiodynamic scan (PDS) and salt spray tests. The results indicate that introducing small amounts of metal cation, Na+ and anions, Cl-, SO42- in the coatings have an influence on the corrosion protection performance. This finding was obtained from salt spray test. The increasing amount of Na+ in the coatings demonstrated lower resistance and high current density from potentiodynamic polarisation tests. Furthermore, the preparation method of coating lacquer solution has an effect on the corrosion resistance properties.