UV radiation effect on the corrosion inhibition potential of Helichrysum kraussii plant extract on mild steel metal in sulphuric acid medium

The comparison of the effect of UV-radiated and non-radiated Helichrysum kraussii (H. kraussii) extracts was studied for mild steel corrosion in 1.0 M H2SO4 at 30–60 °C using Liquid chromatography-mass spectrometry (LCMS), gravimetric weight loss analysis, electrochemical analysis and Fourier Transform Infrared spectroscopy (FTIR). The LCMS confirmed the trans-to-cis shift geometrical isomerisation for H. kraussii due to UV radiation. From the gravimetric analysis data, the corrosion rate was calculated and found to be decreasing with an increase in the concentration of the inhibitor extracts, with the highest concentration at 30 °C having a corrosion rate of 3.920x10-4 and 1.700x10-4 g.cm2.h−1 for UV-radiated. Non-radiated H. kraussii extract gave the highest inhibition efficiency of 96.663 % compared to 92.503 % of the UV-radiated H. kraussii extract. The semi-circles diameter of the Nyquist plot from the electrochemical impedance spectroscopy (EIS) was found to increase with an increase in the inhibitor concentration, suggesting the increase in inhibition with an increase in the concentration of the two extracts. Functional groups such as C = C, O-H, and N-H, known to be functional groups of the most effective corrosion inhibitors, were observed for both extracts from FTIR. Based on the results obtained, it was found that the UV-radiated H. kraussii extract was more effective in inhibiting the corrosion of mild steel in sulphuric acid than the non-radiated H. kraussii extract. This suggests that UV radiation decreases the efficiency of the H. kraussii extract as a corrosion inhibitor for mild steel in H2SO4. Therefore, it is recommended that the H. kraussii extract be used only as a corrosion inhibitor for mild steel in 1.0 M H2SO4 in its original state without being exposed to UV radiation

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