| Summary: | Abstract Artemisia capillaris leaf extract (ACLE) for corrosion inhibition of Q235 steel at 25–65 °C in 1 m HCl was analyzed by weight loss measurements, electrochemical tests, and quantum chemical calculations. Ultra‐high‐resolution electro‐spray time‐of‐flight mass spectrometry was used to determine the major components in ACLE. The results show that ACLE has an obvious corrosion inhibition effect. At 10 g L−1 of ACLE, the corrosion inhibition efficiency can reach 99 % at 25 °C, but the inhibition efficiency decreases with the increase of temperature. Caffeic acid (0.55 wt % in ACLE) is speculated to be a major effective corrosion inhibition component in ACLE. The adsorption of active molecules in ACLE on the Fe surface may involve both physisorption and chemisorption, and however it may incline to physisorption. The adsorption of ACLE on the Q235 steel surface is a spontaneous process and conforms to the Langmuir adsorption isotherm model. The presence of ACLE can obviously increase the apparent activation energy of the dissolution reaction of iron. The combination of ACLE and L‐cysteine has a preferable synergistic inhibition effect, with the optimal mass ratio of ACLE and L‐cysteine of 7 : 3 at 25 °C. This work may provide an alternative strategy for the corrosion inhibition of metals via the synergistic effect of plant extracts with other inhibitors.
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