2.4.7. Scanning Electron Microscopy with Energy-Dispersive X-ray Spectrometry (SEM-EDS)

Two different systems were used during this study. Initial analysis of the crosssections was conducted using a JEOL JSM-6460LV SEM with an Oxford Instruments 80 mm<sup>2</sup> X-MaxN X-ray spectrometer running the Oxford INCA software. The SEM was operated in low vacuum mode at a chamber pressure of 35 Pa, with an operating voltage of 20 kV, beam current circa 1 nA and working distance of 10 mm. The cross-sections were not coated prior to analysis.

More detailed analysis including mapping of the cross-sections and paint films were collected using an FEI Helios 660 Dual-Beam SEM/FIB equipped with an EDAX Octane Plus EDS system, with EDAX TEAM brand acquisition and mapping software. Samples were prepared for imaging by carbon-coating with a layer of amorphous carbon of between 50–100 nm thickness, for electrical discharge purposes. Images were collected using an accelerating voltage of 3 kV, beam current of 3.2 nA. EDS maps were acquired with an accelerating voltage of 15 kV and a beam current of 13 nA.

### **3. Results and Discussion**
