Experimental Investigation of the Hybrid Epoxy-Silane Coating for Enhanced Protection against the Corrosion of Aluminum Alloy AA7075 Frame in Solar Cells

Abstract

The anticorrosion properties of epoxy-silane hybrid coated aluminium (Al) alloy were investigated using electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) in natural seawater. The resistances of charge transfer (Rct) and the film (Rf) of 7075 aluminum alloy had higher values at 1 day, which decreased slowly over the testing time. The release of Al3+ ion into the solution from the surface of the anode and the consumption of oxygen dissolved at the cathode surface was monitored by SECM. It was measured that the Al3+ dissolution was hindered at the scratch of coated 7075 aluminum alloy because of the higher resistance to dissolution of anode. Analysis by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) proved that Mg, Zn, and Cu were enriched at the scratch of coated 7075 Al alloy. The nanometer level layers of oxide containing Mg, Zn, Cu, and Al in 7075 Al alloy were identified by focused ion beam-transmission electron spectroscopy (FIB-TEM) analysis. These accumulated metal complexes possess high corrosion resistance against the corrosion of the coated Al alloy. The hybrid nanocomposite coated 7075 aluminum alloy showed an enhanced protection against the corrosion. The reinforcement of 3-aminopropyltriethoxy silane (APTES) with epoxy coatings resulted in a good adhesion strength, less oxygen permeability, and excellent protection against the corrosion of the coating.