The inhibition efficiency (IE) of an aqueous extract of Hibiscus rosa-sinensis (white) in controlling corrosion of aluminium at pH 12 has been evaluated by weight loss method in the absence and presence of Zn 2+ . The formulation consisting of 8 mL flower extract (FE) and 50 ppm of Zn 2+ had 98% inhibition efficiency. Polarization study revealed that this formulation functioned as cathodic inhibitor. AC impedance spectra revealed the presence of a protective film formed on the metal surface. FTIR spectra revealed that the protective film consisted of a complex formed between the active principle of the flower extract and Al 3+ .

Green synthesis has emerged as a reliable, sustainable and ecofriendly protocol for synthesizing a wide range of nanomaterials and hybrid materials. In this paper, we report the synthesis of Copper oxide nanoparticles by a simple biological route using the extract of Brassica oleracea var. italic and copper (II) acetate as the metal precursor. The synthesized copper oxide nanoparticles were characterized using UV-visible spectroscopy, FTIR spectroscopy, FESEM, EDAX, and XRD techniques. UV -Visible analysis shows a characteristic peak around 220 nm for copper oxide nanoparticles. FTIR spectroscopy was used to characterize various capping and reducing agents present in the plant extract responsible for nanoparticle formation. The surface morphology was characterized using FESEM. The EDAX and XRD pattern suggested that prepared copper oxide nanoparticles were highly pure. The average particle size was calculated as 26 nm using the XRD technique. Further, the nanoparticles were found to exhibit the highest antifungal activity against Aspergillus niger and Candida Albicans.

The inhibition efficiency of Eosin in controlling corrosion of carbon steel immersed in well water, has been evaluated by mass loss method both in absence and presence of zinc ion. A synergistic effect exists between Eosin (EN) and Zn 2+ . The inhibition efficiency (IE) of the EN -Zn 2+ system decreases with increase in immersion period. Addition of N-cetyl-N,N,N-trimethylammonium bromide (CTAB), sodium dodecyl sulphate (SDS), sodium sulphite (Na 2 SO 3 ) does not change the excellent inhibition efficiency of the EN-Zn 2+ system. Polarization study suggests that the EN-Zn 2+ system functions as an anodic inhibitor system. AC impedance spectra reveal the presence of a protective film on the metal surface. FTIR spectra indicate that the protective film consists of Fe 2+ -EN complex and Zn(OH) 2 .

The inhibition efficiency (IE) of K 3 [Fe(CN) 6 ] in controlling corrosion of carbon steel in aqueous solution containing 60 ppm of Clin the presence and absence of Zn 2+ has been evaluated by weight loss method. The formulation consisting of 100 ppm K 3 [Fe(CN) 6 ] and 50 ppm Zn 2+ offers 98% inhibition efficiency to carbon steel immersed in aqueous solution containing 60 ppm Cl -. A synergistic effect exists between K 3 [Fe(CN) 6 ] and Zn 2+ . As immersion period increases, the inhibition efficiency of K 3 [Fe(CN) 6 ]─ Zn 2+ system decreases. Polarization study reveals that this formulation controls the cathodic reaction predominantly. AC impedance spectra reveal that a protective film is formed on the metal surface. FTIR spectra reveal that the protective film consists of Prussian blue and Zn(OH) 2 . The film is found to be UV fluorescent.

The inhibition efficiency of sodium gluconate (SG)-Zn 2+ system in controlling corrosion of carbon steel in sea water has been evaluated by weight-loss method. The formulation consisting of 250 ppm of SG and 75 ppm of Zn 2+ has 98% IE. Influence of duration of immersion on the IE of SG-Zn 2+ has been evaluated. The mechanistic aspects of corrosion inhibition have been investigated by polarization study and AC impedance spectra. The protective film has been analysed by FTIR and luminescence spectra. The surface morphology and the roughness of the metal surface have been analysed by atomic force microscopy. The protective film consists of Fe 2+ -SG complex and Zn(OH) 2 . It is found to be UV -fluorescent.

The inhibition efficiency [IE] of an aqueous extract of eclipta alba leaves in controlling corrosion of carbon steel in sea water [Thondi, Tamil Nadu, India] has been evaluated by weight loss method. The weight loss study reveals that the formulation consisting of 6 mL of EAE (Eclipta Alba extract) and 25 ppm of Zn 2+ has 92% inhibition efficiency in controlling corrosion of carbon steel in sea water. Polarization study reveals that EAE and Zn 2+ system functions as a mixed type inhibitor. AC impedance spectra reveal that a protective film is formed on the metal surface. The nature of the metal surface has been analysed by FTIR spectra and AFM analysis.

The inhibition efficiency of phenolphthalein in controlling corrosion of carbon steel immersed in well water has been evaluated by mass loss method both in absence and presence of zinc ion. A synergistic effect exists between phenolphthalein (PN) and Zn 2+ . The inhibition efficiency (IE) of the PN -Zn 2+ system decreases with increase in immersion period. Addition of N-Cetyl-N, N, N-Trimethylammlonium bromide (CTAB) sodium dodecyl sulphate (SDS), sodium sulphite (Na2SO3) does not change the excellent inhibition efficiency of the PN-Zn 2+ system. Polarization study suggests that the Pn-Zn 2+ system functions as a mixed inhibitor system. AC impedance spectra reveal the presence of a protective film on the metal surface. FTIR spectra indicate that the protective film consists of Fe 2+ -PN complex and Zn(OH)2.

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