Effect of Polar Extract of Cocoa Peels Inhibitor on Mechanical Properties and Microstructure of Mild Steel Exposed in Hydrocloric Acid

Abstract

Effect of addition of theobroma cacao peels extract (TCPE), a new proposed green inhibitor, on tensile and hardness properties, and related microstructure of mild steel exposed in solution of 1.5M HCl was investigated in order to know the contribution of this kind of inhibitor in controlling mechanical properties, in addition to reducing corrosion attack. Corrosion behaviors including inhibition mechanism and adsorption process during exposure were then discussed. Corrosion rate and inhibitory efficiency of mild steel samples containing 0.3%C were determined using weight loss method. The samples were exposed in the acid solution with and without addition of 0.5-2.5% the TCPE. Tensile and hardness tests were subsequently performed on the samples to determine the change of mechanical properties of the metal prior and after addition of the extracts. Sample surface morphologies and chemical composition as well were observed by a scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDX). The results show that the strength, hardness and elongation of mild steel drop significantly due to heavy damage in the surface after immersion in the HCl solution for 32 days. However, these mechanical properties gradually increase with increasing concentration of the extract following the increase of surface coverage and inhibition efficiency. The increase of the tensile properties and hardness is due mainly to the ability of the inhibitor to cover mild steel surface through formation of metal-organo complexes protection layer in the surface of the mild steel. Although total carbon level in the surface of the mild steel also increases significantly, there is no any proof of carbon difussion into the mild steel. The addition of polar extract of theobroma cacao peels into a solution of 1.5 M HCl is, therefore, not only effective to minimize the degradation on the mild steel surface, but it also diminishes the mechanical properties reduction of the mild steel.

ADSORPTION CORROSION INHIBITIVE BEHAVIOR OF PEELS EXTRACT OF Theobroma cacao ON MILD STEEL AS A CORROSION INHIBITOR IN HCl MEDIA

“…3,9 Some fundamental investigation, however, is still necessary to obtain every chemical, physical and mechanical aspects of the applying green inhibitor to protect mild still in a corrosive medium. As reported in the previous article 2,6 the addition of a small amount of Theobroma cacao peels leads to a decrease in the rate of corrosion and increases the usability of inhibitor the steel by 1.5M hydrochloric acid medium. In order to describe the corrosion mechanism in the detail, and the compound that takes part in controlling the inhibition, the extract and corrosion product will be observed by GC-MS and FTIR.…”

“…Changes in the value of b a and b c and Tafel curves presented in the previous article 6 indicate that adsorption of the cacao peels extract is a modification of the anodic dissolution at the anode and the hydrogen evolution at the cathode. Tafel curve is clear that both the cathode and anode reaction inhibited, and the inhibition process in line with the increase in the concentration of TCPE in acidic solution, but more polar in the cathode.…”

“…All of their procedures in this study have been described in a previous article. 2,6 Polarization Resistance (Rp) Corrosion testing using polarization resistance techniques aims to see the resistance of the sample toward oxidation when exposed by the external sources. Polarization resistance is the relevant approach to gauge the rate of corrosion and the usability of inhibition without affecting metals by using Stern-Geary formula the following equation 1: .…”

“…3,4 Therefore, it is necessary to reduce corrosion rate by using inhibitor from natural extract. 4,5,6 Corrosion inhibitor is a chemical compound that is added to a liquid or gas to reduce the corrosion. 5 Inorganic inhibitors are commonly used up to now such as chromate, phosphate, molybdate and others.…”

Synthesis of Cuprum (Cu) Layer by Electrodeposition Method with Theobroma cacao Peels as Corrosion Protector of Steel

“…Common corrosion inhibitors exist that are inorganic and organic in nature [6]. Using of inorganic inhibitors to slow the rate of corrosion has several disadvantages, because they contain hazardous chemicals to living things, they are relatively expensive, and they are not environmentally friendly [1], [7], [8], [9], then inhibitors made from natural ingredients are the answer to this problem, such as coriander leaves [10], Aloe vera leaves [11], [12], Theobroma cacao peels without combine with electrodeposition method [13]. Theobroma cacao is an abundant natural resource in Indonesia.…”