Polyester based-siloxane modified waterborne anticorrosive hydrophobic coating on copper

Polyester-based, polydimethylsiloxane (PDMS) modified waterborne, thermal cured hydrophobic coating was developed for corrosion protection of copper using hexa(methoxymethyl)melamine (HMMM) as a cross-linker and para-toluene sulphonic acid (p-TSA) as catalyst. The cross-linking ratio for polyester resin and HMMM was fixed based on preliminary studies to 70:30, based on FTIR-imaging and DSC studies. The coatings were applied on pre-treated copper panels by dipping method and were cured at 160 °C for 20 min. Electrochemical performance of the modified coating was investigated and compared with neat polyester coating using potentiodynamic polarization study and exposing the coated samples to salt spray environment and UV weathering. The structural and morphological features of the coating before and after exposure to the test environment were analyzed using atomic force microscopy (AFM) and scanning electron microscopy (SEM/EDAX). Mechanical properties like, the hardness and scratch resistance of the coatings were determined by nano-indentation and nano-scratch tester respectively. Hydrophobic property of the coating was determined by contact angle measurement. The siloxane modified coating was found to have improved electrochemical and mechanical properties along with excellent hydrophobicity, as compared to the neat polyester coating.