Carica papaya leaf extract (CPLE) as green corrosion inhibitor for AISI 4140 steel in 15% hydrochloric acid medium

Abstract

This study investigated the potential of Carica papaya leaf extract (CPLE) as the corrosion inhibition and un-inhibition of AISI 4140 steel tubing in a 15% HCl acidizing oilfield environment. The C. papaya leaf was extracted using continuous extraction method with ethanol. The selected mild steel elemental compositions were determined using atomic mass spectrometry analyzer. Process modeling and optimization of process condition was carried out by response surface methodology impose central composite rotatable design (RSM-CCRD) and artificial neural network impose genetic algorithm (ANN-GA) with constraint variables: inhibition conc.; X1, immersion time; X2, and temperature; X3, respectively. The thermodynamic parameters were evaluated using corrosion rate and transitional state equations, while the fitness of absorption isothermal study was examined via Langmuir, Temkin, Frumkin, and Flory-Huggin equations.Results shows that iron (Fe) is the predominant element in the alloy steel used in this study with other elements present in small quantities. Statistical analysis by RSM-CCRD validated the minimum CR and optimum IE yields of 35.90 (mm/yr) and 69.54%, while ANN-GA validated the minimum CR and optimum IE yields of 26.10 (mm/yr) and 69.82%, respectively. Based on thermodynamic parameter, the Gibb's free energy change of absorption was negative and fell within the thresholds of chemisorptions. The fitness of absorption was established by Langmuir isotherm.The study concluded that the modeling and optimization of absorption of CPLE on AISI 4140 steel in 15% HCl medium is feasible and can be used in the industries.

Keywords

• C. papaya leaf
• Inhibition
• AISI 4140 steel
• Adsorption
• Chemisorptions
• Response surface methology