Synergistic inhibition effects of bamboo leaf extract/major components and iodide ion on the corrosion of steel in H3PO4 solution

• There are synergisms between DSCLE, rutin and orientin with I− for steel in H3PO4.
• There is a stronger synergism for crude extract compared with two major components.
• The adsorption of DSCLE without and with I− obeys Langmuir isotherm.
• DSCLE is a cathodic inhibitor, while mixed-type inhibitor for DSCLE/I−.
• The adsorption center of rutin and orientin is falvones backbone structure (FBS).

The synergistic inhibition effects of the bamboo of Dendrocalmus sinicus Chia et J.L. Sun leaf extract (DSCLE)/major compounds (rutin and orientin) and iodide ion (I−) on the corrosion of cold rolled steel (CRS) in 0.1 M H3PO4 solution at 25–60 °C was studied by weight loss, potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS) and quantum chemical calculation methods. DSCLE and two major compounds act as moderate inhibitors, and inhibition efficiency follows the order: DSCLE > rutin > orientin. However, incorporation of them with I− significantly improved the inhibition performance, and produced strong synergistic inhibition effect.