Synergistic inhibition between naturally occurring exudate gum and halide ions on the corrosion of mild steel in acidic medium

The effect of naturally occurring exudate gum from Raphia hookeri (RH) on the corrosion of mild steel in H₂SO₄ in the temperature range 30-60°C was studied by weight loss and hydrogen evolution techniques. Results obtained reveal that the exudate gum reduces the corrosion rate. The inhibition efficiency increased with an increase in exudate gum content up to 5g/l to reach 70% at 30 °C and decreases with increase in temperature. The adsorption of exudate gum from Raphia hookeri on the mild steel follows Langmuir adsorption isotherm. Results obtained by weight loss and hydrogen evolution technique are in good agreement. The addition of halide ions to the exudate gum enhanced the inhibition efficiency due to synergistic effect. Mechanism of physical adsorption is proposed from the apparent activation energy (E_a) and the thermodynamic parameters obtained. The adsorption of the exudate gum on the mild steel surface is spontaneous.