Isotemp digital stirring hotplate

The WAS samples were heated at 80 °C and stirred at 600 rpm using a Fisher Scientific™ Isotemp™ Digital Stirring Hotplate. The samples were heated for EPS extraction and to evaporate 80% of water from the WAS samples. Heating is a physical method of EPS extraction. Furthermore, the relatively low temperature of heating minimizes the degradation of temperature labile compounds. Samples were then cooled down to room temperature and centrifuged at 1,207×g for 5 min. Then, the supernatant was collected and frozen for 24 h at −20 °C, followed by thawing for another 24 h. The freeze-thaw process was repeated five times before the supernatant was deemed as an EPS mixture for corrosion inhibition testing.

Experiments under pressure were performed in a pressure vessel (Series 4600-1L-VGR with single inlet valve, Parr Instrument Company), pressurised with N₂ gas and placed on a hotplate (Fisherbrand Isotemp Digital Stirring Hotplate) at 30°C. Samples for both the high pressure experiment and ambient pressure control experiment were prepared in 2 mL glass headspace vials (Agilent Technologies) whose caps were pierced with a needle.