Adsorption behavior of scent leaf extract as corrosion inhibitor for carbon steel in natural sea water

Abstract

The research was centered on corrosion inhibition and adsorption mechanism of scent leaf extract, on carbon steel, in natural sea water environment. Six different concentrations of scent leaf extract (0.1, 0.2, 0.4, 0.6, 0.8 and 1.0 g/L) were prepared using sea water collected from the Lagos bar beach, South-Western Nigeria. The seventh environment was sea water without the leaf extract, acting as control. The gravimetric method based on ASTM G-31 was used to study the corrosion behavior of the carbon steel in the presence and absence of the scent leaf extract. The study was conducted at 308 K, 318 K, 328 K, 338 K and 348 K, and at periodic intervals of 10 h, 15 h and 20 h. Findings from the investigation, reveal that the corrosion rate was lower in the environments, containing the scent leaf extract. It also decreased with increase in time, concentration and temperature. Thus, inhibition efficiency increased as a function of increase in concentration and time, reaching the highest value of 96.4% in 20 h, at 308 K. The activation energy (Ea), change in enthalpy (∆H) and entropy (∆S), were lowest in the reference medium and increased with increase in the extract concentration and time. Change in Gibb’s free energy of adsorption (∆Gads) was negative for all the investigated temperatures and greater than – 20 kJ·mol– 1. Its value also decreased with increase in temperature. The study concludes that scent leaf extract could be an effective corrosion inhibitor for carbon steel, in natural sea water as its adsorption was realistic, spontaneous and followed physisorption.