Sustainable Corrosion Inhibition of Carbon Steel With Sodium Silicate

Cooling water systems are frequently used to control process temperature in industrial applications. To avoid performance issues due to material degradation, corrosion inhibitors are added. As a consequence, these chemicals are partly removed from the system in a blowdown and end up in the surface water bodies. Aiming to conserve aqueous ecosystems, this work investigates sustainable green corrosion inhibitors for cooling water applications. The inhibition efficiency of sodium silicate (SiO2:Na2O = 3) is evaluated for S235 carbon steel submerged in a 3 wt.% NaCl environment under dynamic conditions. A set environment is controlled with a rotating cylinder electrode (RCE) with external heating while potentiodynamic scans (PDS) and electrochemical impedance measurements (EIS) are executed. Both PDS and EIS point out that an increasing silicate dosage results in a higher inhibition efficiency (IE), reaching a maximum of 98.61% and 99.78% for PDS and EIS respectively at 10 mM Na2Si3O7 at 25 °C, whilst maintaining a constant rotation speed of 0.5m/s (surface speed). An increase of temperature (to 35°C) leads to a decrease in IE at a constant rotation speed. Finally, variation of flow speed yields mixed findings: EIS shows an increase in IE, reaching a maximum towards 0.75 m/s and decreasing slightly towards higher speeds (>=0.875 m/s).