ABSTRACT

The adsorption mechanism was confirmed to be physical and spontaneous. Adsorption isotherms like Langmuir adsorption isotherm, Freudlich adsorption isotherm, and Temkin adsorption isotherm were used to examine the adsorption behavior of the plants extracts, and the adsorption was discovered to fit into all the adsorption isotherms but best fitted in Langmuir adsorption isotherm. The results obtained show that both plant extracts reduced corrosion rate of mild steel in 2.5M HC1 solution. The range of inhibitor efficiency obtained from gravimetric analysis are 83.94% to 97.06% and 74.80% to 99.00% for Piper guineense and Vernonia amygdalina leaves extracts respectively. The values of inhibition efficiency obtained from the gasometric analysis ranges from 80.47% to 99.70% and 75.74% to 99.4 1% for Piper guineense and Vernonia amygdalina leaves extracts. While it's thermometrically determined inhibition efficiency ranges from 71.25% to 96.57% and 35.63% to 92.70% for Piper guineense and Vernonia amygdalina extracts respectively. The reduction in Corrosion rates were observed to be more pronounced as the concentration of the plant extracts increased from 0.lg/1 to 0.5g/l. The inhibition efficiency increases as the concentration of the plant extracts increases, but reduces as temperature of the system rises. The inhibitory effect was deduced to be as a result of the extract molecules adsorption on the surface of the mild steel which creates a barrier between the acid and the mild steel, hindering corrosion within the covered area.