# Recent Trends and Progress in Corrosion Inhibitors and Electrochemical Evaluation
## 6 Recent Trends and Developments in Corrosion Inhibitors  
Nowadays, a variety of environmentally acceptable substitutes made from natural resources, such as biopolymers, plant extracts, and chemical medications (drugs), are frequently used in place of hazardous corrosion inhibitors. A number of biopolymers are also frequently utilized as environmentally safe corrosion inhibitors in both their pure and modified forms. Substances synthesized by multicomponent reactions (MCRs), as well as microwave (MW) and ultrasonic (US) irradiations, are also thought to be environmentally safe. Recently, environmentally friendly methods have received a lot of attention. These methods include the use of rare earth metals (REM), polyfunctional compounds, synergistic use of organic and inorganic compounds with REM, and encapsulation of inhibitors. These methods are obviously associated with low to no toxicity and high levels of protection effectiveness [169]. In particular, Monte Carlo simulations, molecular dynamics, and density functional theory (DFT) have lately become powerful computational chemistry methods for corrosion monitoring. Contrary to expensive experimental methods, computational modeling uses computer software to anticipate inhibitory efficiency and is also environmentally friendly [170]. The primary purpose of a DFT study is to compare the relative inhibitory effects of a number of molecules with identical chemical structures. High inhibitory efficiency instruments are typically related with greater EHOMO, softness (s), and dipole moment (m) values as well as lower ELUMO, electronegativity (c), and hardness (h) values [170]. The organic compound N, N, 1-tri(oxiran-2-ylmethoxy)-5-((oxiran-2-ylmethoxy)thio)-1H-1,2,4-triazoleol-3-amine (TTA) is used as a CI in the corrosive media 1 M HCl in carbon steel C38. The inhibition studies were performed using EIS, PDP, and theoretical calculation conducted via DFT and MD simulations [171]. Papaver somiferrum (P. somiferrum) seed  
Figure 21: MS Tafel polarization graphs in varied spermidine concentrations in (**a**) 1 M HCl and (b) 0.50 M H\({}_{2}\)SO\({}_{4}\)[168]. extract was used to test the iron alloy's corrosion resistance in 0.5 M sulphuric acid. Notably, at 500 mg/L concentration, [PERSON] et al. [172] used a soybean oil-based CI on steel alloy and efficiency was tested by DFT. [PERSON] et al. [6] synthesized nanocrystalline cellulose (CEL) and nanocrystalline cellulose (NCC) and tested it as a CI. The anticorrosive properties of CEL and NCC polymers were intended to be displayed via density functional theory (DFT) parameters. Somniferum demonstrated 95% corrosion resistance efficiency. Adsorption and phytochemical studies were carried out via DFT. Papaver somniferum has three phytochemicals, namely papaverine, narcotine, and thebaine. The optimized HOMO and LUMO orbitals of the aforementioned phytochemicals are shown in Figure 22[173]. Highly concentrated acidic solutions are used in a variety of industrial operations [174; 175; 176]. Acid pickling is one of the most significant and well-known acidic processes, and it involves removing rust and other surface impurities from metal plates, wires, pipelines, and other metal equipment from various industrial sectors, including heat exchange, heat transfer, cooling system, and boiler industries. Most of the previously employed industrially useful corrosion inhibitors are not ecologically friendly due to their harmful nature and manufacturing using risky chemicals and solvents. However, the use of environmentally friendly materials derived from eco-friendly synthetic techniques and natural resources should be encouraged due to rising ecological consciousness and severe environmental restrictions. The adoption of environmentally friendly biopolymer-based CIs would be recommended due to increasing ecological awareness and environmental awareness and environmental restrictions [177; 178; 179]. There have been numerous reports on the anticorrosive properties of chitosan's for metals and alloys [178; 179].