Abstract
In this work, the aqueous Lawsonia inermis extract (LI) is investigated as an economic and green deterioration inhibitive formula for steel alloy 4130 in 3.5 wt.% NaCl solutions. The water-based extraction process is considered as one of the cheapest techniques for preparation of active ingredients of natural products. These ingredients play an important role in corrosion mitigation of steel alloy 4130 in saline media. This extract was subjected to three different parameters: inhibitor concentration, rotation speed, and temperature in 3.5 wt.% NaCl solutions. The electrochemical techniques are used to perceive the corrosion behavior, and the obtained results were dedicated to theoretical explorations to assess the features of corrosion inhibition and the adsorption over the steel substrate in 3.5 wt.% NaCl solutions. Affording to the electrochemical techniques of LI showed very promising results against corrosion depending on the inhibitor concentrations. The inhibition efficiency of LI was additionally appraised at three diverse temperatures, and the results disclosed that the inhibition efficiency is decreased. Additionally, the theoretical aspects illuminated that the main active ingredients of LI have a proclivity to coagulate on the steel substrates allowing these areas to paradigm a protecting layer on the steel surfaces. This behavior is in provision of investigational results. Statistical studies were used to examine the consequence of chief constraints (i.e., inhibitor concentration, temperature, and rotation speed) on the inhibition efficiency and the rate of corrosion of steel alloy 4130. The inhibitive effect of LI in contradiction of the corrosion of steel alloy 4130 surfaces is considered by resources of DFT/6-31G(d) calculations. The quantum chemical parameters interrelated to the inhibition efficiency are considered.
Highlights
3.5 wt.% NaCl solutions are commonly utilized in various investigations due to the broad-spectrum existence in industrial zones [1]
Inhibition possessions of Lawsonia inermis extract (LI) were inspected on the steel alloy 4130 electrode (1 cm × 1 cm) with composition as mentioned in Table 1. e electrodes were graceful using SiC papers. e refined sample was washed away with bidistilled water and formerly dried out. e destructive 3.5 wt.% NaCl solutions protected by LI at several concentrations were equipped by NaCl (Merck Co.) and bidistilled water
Water is used a proper solvent for the two main reasons: (i) make the extraction process cost-effective and environmentally acceptable; (ii) only the water-soluble components can be extracted from Lawsonia inermis during the water extraction process. ese complexes do not demonstrate good controlling rate in destructive media. 100 g/100 ml distilled water of Lawsonia inermis powder was poured into 1000 ml beaker, boiled for 30 min, and filtered, and the filtrate is concentrated to 100 ml. e resulting clear solution was used for preparation of the examination electrolytes in electrochemical studies. e major existing compound in LI is 2-hydroxy-1,4-napthoquinone (HNQ; lawsone)
Summary
3.5 wt.% NaCl solutions are commonly utilized in various investigations due to the broad-spectrum existence in industrial zones [1]. It has been verified that the organic compounds including atoms such as N, O, P, and S in extra exist in aromatic rings and binary or tripartite bonds All these factors can make the organic molecule to act as efficient corrosion inhibitors. With a concentration of about 1000 ppm, it shows an inhibition efficiency of about 93% for protection of mild steel in acidic solution [15]. E root of Glycyrrhiza glabra is applied as green corrosion inhibitor with 99% inhibition efficiency after immersion of steel coupon for 72 h in 3.5 wt.% NaCl solution. By bearing in mind these aspects, the present study was planned to use the aqueous Lawsonia inermis extract (LI), which is cost-effective, for monitoring the decomposition of mild steel alloy 4130 in 3.5 wt.% NaCl solutions. Remarkable found that the oxygen containing compound, which promotes more inhibiting activity, is among diverse ingredients of LI
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