Abstract
The corrosion inhibition of mild steel in 1M sulphuric acid solution by the ethanol extract of Commelina benghalensis (C. B) leaves was determined using gravimetric technique. Phytochemical analysis was carried out on the extract and the effect of extract concentration, temperature, immersion time and acid concentration on the corrosion process was determined. The corrosion inhibition efficiency of the extract increased with increase in the concentration of the extract and decreased with increase in temperature. Increase in temperature also increased the corrosion rate of mild steel in 1M sulphuric acid in the absence and presence of different concentrations of the extract. The adsorption of the plant extract obeyed Langmuir and Freundlich adsorption isotherms. The process of physical adsorption was proposed for the extract from the trends of inhibition efficiency with temperature and from calculated values of Gibbs free energy, activation energy and enthalpy of adsorption. Gibbs free energy values for the reactions were less than 20kJ/mol, indicating physical adsorption process and were also found to be negative, indicating that the adsorption process was spontaneous. The corrosion inhibition efficiency (% IE) of the plant extract was attributed to the phytochemical constituents (alkaloids, flavonoids, tannins, saponins, phenolics, steroids and cardiac glycosides) present in them. The results showed that Commelina benghalensis can serve as a good corrosion inhibitor of mild steel in acid medium, since it reached a corrosion inhibition efficiency (% IE) of 91.91% at 2.0g/L extract concentration.
Highlights
Corrosion is commonly defined as the deterioration or wearing off of metals due to chemical reactions, but in more scientific meaning it is a physiochemical interaction between any exposed metal and its surrounding environment that results in the formation of an oxide called rust
In view of our interest in environmentally friendly corrosion inhibitors, this present study investigates the inhibitive effects of Commelina benghalensis leaves extract on the corrosion of mild steel in 1M sulphuric acid (H2SO4) solution
The corrosion inhibition efficiency of the plant extract could be due to their phytochemical constituents which aided their adsorption on the surface of the mild steel
Summary
Corrosion is commonly defined as the deterioration or wearing off of metals due to chemical reactions, but in more scientific meaning it is a physiochemical interaction between any exposed metal and its surrounding environment (e.g. oxygen) that results in the formation of an oxide called rust. Corrosion of metals remains a global scientific problem as it affects the metallurgical, chemical, food processing and oil industries. It is invariably present in most industries whose facilities are constituted by metallic structures. In the application of these inhibitors for corrosion control they were found to be expensive, toxic, carcinogenic, non-biodegradable and environmentally unfriendly This made the investigation and ongoing trend of finding safe, cheap, biodegradable, renewable and environmentally friendly corrosion inhibitors like plant extracts of great importance to many industries. In view of our interest in environmentally friendly corrosion inhibitors, this present study investigates the inhibitive effects of Commelina benghalensis leaves extract on the corrosion of mild steel in 1M sulphuric acid (H2SO4) solution
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