Evaluation of polyphenol composition and anti-corrosion properties of Cryptostegia grandiflora plant extract on mild steel in acidic medium

•Cryptostegia grandiflora extract inhibited mild steel corrosion in 1M H2SO4.•Phenolic and flavonoid compounds were found to be the active ingredients.•XRD studies clearly revealed the formation of a complex.•SEM-EDX results indicated the formation of a protective film on the mild steel. The total phenolic and flavonoid compounds present in Cryptostegia grandiflora leaf extract were analyzed. The results confirmed that the extract contains the Myricetin 3582.22(μg/g) and Rutin 45.62(μg/g) as major components. C. grandiflora extract was evaluated for its anti-corrosion property on mild steel in 1M H2SO4. A maximum inhibition efficiency of 87.54% was achieved by using 500ppm of the inhibitor. Polarization studies indicate that the extract acts as a mixed inhibitor. The formation of productive layer on mild steel by inhibitor was confirmed by SEM-EDS and AFM. The extract is adsorbed on the mild steel according to Temkin adsorption isotherm.