In-situ study of interfacial bonding degradation of polyester coating on multi-metal oxides

The need for thinner, weight-saving coatings together with the aim of conserving limited natural resources, create a high industrial interest in reducing the amount of zinc used in galvanized steel. Alloying zinc with aluminium and magnesium significantly enhances the corrosion resistance allowing the use of thinner coatings.1 Other sectors attracted by magnesium and aluminium are the automotive and aerospace industry which benefit from the high stiffness to weight ratio. This work is a comparative study, relating zinc, magnesium and aluminium oxide properties to the adhesion of ester-functionalized molecules. Firstly, Dimethyl succinate is used to mimic the functional groups of widely used polyester coatings. Chemisorption of the ester-functionalized molecules on metal oxides are elucidated using ATR-FTIR in a Kretschmann geometry. The use of monomer model compounds allows the use of surface sensitive techniques, such as XPS, to confirm the elucidated chemisorption mechanisms. Subsequently, the interfacial bonding mechanisms are validated using well defined model polyester coatings. Finally, the durability of the metal oxide - polymer bonds in the presence of water are studied in-situ by ATR-FTIR and EIS in a Kretschmann geometry. Combining these two techniques provides complementary information about the degradation of the metal–polymer system.2,3 ATR-IR provides chemical information related to interfacial adhesion and delamination processes. Supplementary, semi-quantitative accumulation of water in the interfacial region is monitored. On the other hand, water penetration through the bulk polymer and formation of corrosion products at the metal-polymer interface are more easily identified by EIS.