Corrosion Inhibition of Sodium Silicate with Nanosilica as Coating in Pre-Corroded Steel

Marish S. Madlangbayan (Department of Civil Engineering, University of the Philippines Los Baños, Laguna 4031,)
Carlo Nico B. Diola (Department of Civil Engineering, University of the Philippines Los Baños, Laguna 4031,)
Alvin Karlo G. Tapia (Institute of Mathematical Sciences and Physics, University of the Philippines Los Baños, Laguna 4031,)
Milagros M. Peralta (Institute of Chemistry, University of the Philippines Los Baños, Laguna 4031,)
Engelbert K. Peralta (Institute of Agricultural and Biosystems Engineering, University of the Philippines Los Baños, Laguna 4031,)
Ronaniel A. Almeda (Institute of Agricultural and Biosystems Engineering, University of the Philippines Los Baños, Laguna 4031,)
Maris Asuncion L. Bayhon (Institute of Agricultural and Biosystems Engineering, University of the Philippines Los Baños, Laguna 4031,)
Marloe B. Sundo (Department of Civil Engineering, University of the Philippines Los Baños, Laguna 4031,)

Civil Engineering Journal
Vol 7, No 11 (2021): November

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