The adsorption characteristics and synergistic inhibition between polyethylene glycol and halide ions for the corrosion of mild steel in acidic medium

The inhibitory action of polyethylene glycol (PEG) on the corrosion of mild steel in H₂SO₄ was investigated using weight loss, hydrogen evolution and thermometric methods at 303-333K. The effect of halides namely: KCl, KBr and KI is also reported. It was found that PEG acted as an inhibitor for mild steel corrosion in acidic medium. Inhibition efficiency increases with increase in PEG concentration. Addition of halides also increases the inhibition efficiency to a considerable extent. An increase in temperature led to increase in the corrosion rate and inhibition efficiency in the absence and presence of inhibitors and halides. The inhibition efficiency (%I) and degree of surface coverage (0) increased in the order: KI > KBr > KCl, which indicates that the radii and the electro negativity of the halide ions play a significant role in the adsorption process. The values of the synergism parameter, S_I obtained are greater than unity, which suggest that the enhanced inhibition efficiency is only due to synergism. PEG obeys Freundlich, Langmuir and Temkin adsorption isotherms. Phenomenon of chemical adsorption is proposed and the thermodynamic parameters suggest that the adsorption process is spontaneous.