Neem leaf extract as a sustainable green inhibitor for corrosion inhibition in RCC and strength improvement in concrete, in conjunction with spectroscopic characterization and statistical evaluation

The demand for sustainable and environmentally benign green corrosion inhibitors (GCIs) for reinforced cement concrete (RCC) has increased due to the persistent occurrence of corrosion in concrete structures constructed in marine environments. In this study, the influence of neem extract on the strength enhancement of concrete was evaluated through mechanical testing, while its corrosion inhibition performance was assessed in reinforced cement concrete (RCC) samples exposed to 1M NaCl solution. This RCC based corrosion evaluation using neem leaf extract has not been previously reported. Compressive strength and electrochemical tests (Tafel, LPR, and EIS) were carried out for control, 11 ml and 29 ml neem extract containing samples. The 29 ml neem extract containing samples showed higher average strength than the control specimens, validated via SEM analysis which exhibited better CSH gel growth. From Tafel and LPR, the least corrosion rate (0.3759 mm/year) and highest polarization resistance (1647.9 Ω) was attained for the highest inhibitor concentration. The EIS outcome for all samples displayed Warburg impedance, along with a decrease in the double-layer capacitance with increasing neem concentration. The energy parameter values of phytochemical compounds in neem obtained via DFT showed strong concurrence with the statistical output of the principal component analysis (PCA). The significant compounds present in neem extract were detected using GC-MS. With neem leaves being widely available with less demand throughout the year, non-toxic, eco and environment-friendly, it can be used as a partial replacement in concrete to achieve better strength and durability.