TY - JOUR
T1 - Natural organic antioxidants from green tea form a protective layer to inhibit corrosion of steel reinforcing bars embedded in mortar
AU - Pradipta, Ivan
AU - Kong, Daniel
AU - Tan, Joash Ban Lee
PY - 2019/10/10
Y1 - 2019/10/10
N2 - In our previous work, we have demonstrated that at equal volume, green tea extract (GT) exhibited a higher inhibition efficiency (IE) than commercial calcium nitrite corrosion inhibitor, on corrosion of steel reinforcing bar (rebar) embedded in mortar (75–80 vs. 14–24%). GT behaved as a mixed-type corrosion inhibitor which increased rebar polarization resistance (Rp); indicating that it formed a protective layer on rebar surface. In this paper, the formation of a protective layer was confirmed with visual inspection and microscopic examinations. In presence of this layer, rebar corrosion was reduced. This is evidenced by a reduced rebar weight loss and further indicated by a similar chloride permeability between control and GT concrete, and a similar corrosion rate (CR) between control reinforced mortar and reinforced mortar incorporating solely the residual solid of GT. The similarities ruled out the plausible higher IE of GT due to an improved physical barrier of mortar/concrete against corrosion. Analyses with energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction spectroscopy (XRD), and Fourier-transform infrared spectroscopy (FTIR) suggested that the layer was enriched with calcium, specifically the calcium carbonate polymorphs. Although the formation of protective layer and increase in Rp were influenced by the magnitude of antioxidant activity, in this study GT has shown a better IE than CI. This should encourage more studies on the IE of sustainable ‘green’ corrosion inhibitors in concrete.
AB - In our previous work, we have demonstrated that at equal volume, green tea extract (GT) exhibited a higher inhibition efficiency (IE) than commercial calcium nitrite corrosion inhibitor, on corrosion of steel reinforcing bar (rebar) embedded in mortar (75–80 vs. 14–24%). GT behaved as a mixed-type corrosion inhibitor which increased rebar polarization resistance (Rp); indicating that it formed a protective layer on rebar surface. In this paper, the formation of a protective layer was confirmed with visual inspection and microscopic examinations. In presence of this layer, rebar corrosion was reduced. This is evidenced by a reduced rebar weight loss and further indicated by a similar chloride permeability between control and GT concrete, and a similar corrosion rate (CR) between control reinforced mortar and reinforced mortar incorporating solely the residual solid of GT. The similarities ruled out the plausible higher IE of GT due to an improved physical barrier of mortar/concrete against corrosion. Analyses with energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction spectroscopy (XRD), and Fourier-transform infrared spectroscopy (FTIR) suggested that the layer was enriched with calcium, specifically the calcium carbonate polymorphs. Although the formation of protective layer and increase in Rp were influenced by the magnitude of antioxidant activity, in this study GT has shown a better IE than CI. This should encourage more studies on the IE of sustainable ‘green’ corrosion inhibitors in concrete.
KW - Antioxidant activity
KW - Chloride permeability
KW - CR
KW - EDX
KW - FTIR
KW - Microscopic examinations
KW - Protective layer
KW - Rp
KW - Weight loss
KW - XRD
UR - http://www.scopus.com/inward/record.url?scp=85067310145&partnerID=8YFLogxK
U2 - 10.1016/j.conbuildmat.2019.06.006
DO - 10.1016/j.conbuildmat.2019.06.006
M3 - Article
AN - SCOPUS:85067310145
SN - 0950-0618
VL - 221
SP - 351
EP - 362
JO - Construction and Building Materials
JF - Construction and Building Materials
ER -