Abstract
This study was conducted to investigate the potential of using sodium silicate with nanosilica as a treatment to inhibit the progress of corrosion in steel specimens that are already corroded. Steel specimens measuring 16 mm in diameter and 4 mm in thickness were prepared and subjected to pre-corrosion by immersion to 3.5% NaCl solution. Two sets of specimens were then dip-coated with sodium silicate containing nanosilica. One set was coated with 1% nanosilica, and the other was coated with 2.5% nanosilica. The coated specimens were then subjected to Complex Impedance Spectroscopy (CIS) at 20 Hz to 20 MHz frequency range. Compared with the sodium silicate coating with 1% nanosilica, the sodium silicate coating with 2.5% nanosilica had a larger semi-circle curve in the Nyquist plot. Similarly, the sodium silicate coating with 2.5% nanosilica also showed larger magnitudes of impedance at the low-frequency region and larger phase angles at the high-frequency regions in the Bode plot. These results imply that the sodium silicate coating with 2.5% nanosilica coating demonstrated better capacitive behavior. In addition, equivalent circuit modelling results also showed that the sodium silicate coating with 2.5% nanosilica had higher coating resistance and lower coating capacitance as compared to the sodium silicate coating with 1% nanosilica. Doi: 10.28991/cej-2021-03091761 Full Text: PDF
Highlights
Corrosion is an electrochemical action that is primarily due to chloride ingress
Both the Nyquist plot and Bode plots provided evidence that the sodium silicate with 2.5% nanosilica derived from Rice Hull Ash (RHA) has prevented the progress of corrosion in coated steel plates
The Nyquist plot for the sodium silicate with 2.5% nanosilica exhibited a semi-circle with a larger diameter than the semicircle plotted using the coating with only 1% nanosilica
Summary
Corrosion is an electrochemical action that is primarily due to chloride ingress. Corrosion of structural elements affects different structures in various ways. Corrosion products or rust accumulate as corrosion-causing contaminants enter the concrete and reach the reinforcing steel bars. These accumulated corrosion products cause internal stress which leads to concrete cracking or spalling. Corrosion in steel structures causes reduction in the area of the structural members, leading to lower resistance to stresses [1]. Damages that are caused by corrosion are approximately $276 billion per year [2]. With a 17.8% increase in the price index of steel from 2012 to 2018 [4], protection of existing structures against corrosion damages has been the more viable option over reconstruction
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