Organic Compounds as Corrosion Inhibitors for Carbon Steel in HCl Solution: A Comprehensive Review

Abstract

Most studies on the corrosion inhibition performance of organic molecules and (nano)materials were conducted within "carbon steel/1.0 M HCl" solution system using similar experimental and theoretical methods. As such, the numerous research findings in this system are sufficient to conduct comparative studies to select the best-suited inhibitor type that generally refers to a type of inhibitor with low concentration/high inhibition efficiency, nontoxic properties, and a simple and cost-economic synthesis process. Before data collection, to help readers have a clear understanding of some crucial elements for the evaluation of corrosion inhibition performance, we introduced the mainstay of corrosion inhibitors studies involved, including the corrosion and inhibition mechanism of carbon steel/HCl solution systems, evaluation methods of corrosion inhibition efficiency, adsorption isotherm models, adsorption thermodynamic parameters QC calculations, MD/MC simulations, and the main characterization techniques used. In the classification and statistical analysis section, organic compounds or (nano)materials as corrosion inhibitors were classified into six types according to their molecular structural characteristics, molecular size, and compound source, including drug molecules, ionic liquids, surfactants, plant extracts, polymers, and polymeric nanoparticles. We outlined the important conclusions obtained from recent literature and listed the evaluation methods, characterization techniques, and contrastable experimental data of these types of inhibitors when used for carbon steel corrosion in 1.0 M HCl solution. Finally, statistical analysis was only performed based on these data from carbon steel/1.0 M HCl solution system, from which some conclusions can contribute to reducing the workload of the acquisition of useful information and provide some reference directions for the development of new corrosion inhibitors.

Keywords: 1.0 M HCl; carbon steel; corrosion inhibition performance; evaluation method; statistical analysis.

Figure 1

Diagrammatic illustration of the three adsorptions (physisorption, chemisorption, and retro-donation mechanisms) of organic corrosion inhibitors (DHATs). (Reprinted with permission from Ref. [45]. Copyright 2015 Elsevier Publications).

Figure 2

HOMO orbital, LUMO orbital and ΔE of the three inhibitors (chitosan (CS), neutral (SCSB), and pronated salicylayde-chitosan Schiff Base (SCSB-Protonated)). (Reprinted with permission from Ref. [100]. Copyright 2020 Elsevier Publications).

Figure 3

Optimized geometry structures, HOMO and LUMO plots of the three Schiff-base molecules calculated by the B3LYP method, with the SV(P) and SV/J levels of the basis set. (Reprinted with permission from Ref. [111]. Copyright 2016 Royal Society of Chemistry Publications).

Figure 4

MEP maps of the three inhibitors (2-amino-1,3,4-triazole (AT), 3-(2-pyridyl)-2-amino-1,3,4-triazole (2-AT) and 3-(4-pyridyl)-2-amino-1,3,4-triazole (4-AT)) calculated by B3LYP/6-311 + (2d,p) level. (Reprinted with permission from Ref. [113]. Copyright 2016 Elsevier Publications).

Figure 5

Mode of adsorption of (5-fluoro-2-(methylthio)pyrimidine-4-yl)(piperidine-4-yl)-2,5-dimethoxybenzene sulfonamide (FMPPDBS) on different iron surfaces. (Reprinted with permission from Ref. [127]. Copyright 2016 Elsevier Publications).

Figure 6

The stable adsorption configurations of DTO, STA, and LGS molecules on the Fe (110) surface. (Reprinted with permission from Ref. [130]. Copyright 2020 Elsevier Publications).

Figure 7

RDF analysis of two quinoxaline derivative inhibitor molecules (Q1 and Q2) on the Fe (110) surface in simulated solution, (a) Fe-heteroatoms of Q1, (b) Fe-heteroatoms of Q2, and (c) Fe-inhibitors. (Reprinted with permission from Ref. [134]. Copyright 2020 MDPI Publications).

Figure 8

SEM image of mild steel surface, (a) freshly polished mild steel surface, (b) mild steel surface after 4 h of soaking in 1.0 M HCl, (c,d) mild steel surface after 4 h of soaking in 1.0 M HCl in the presence of 5 mM L-cysteine and D-penicillamine, respectively. (Reprinted with permission from Ref. [139]. Copyright 2020 Elsevier Publications).

Figure 9

Simplified schematic representation of the physical structure of gemini surfactant: (a,b) are gemini surfactants with rigid and flexible spacers, (c,d) are gemini surfactants with short chain and long chain spacers, (e,f) are gemini surfactants with polar and nonpolar spacers, and (g,h) are gemini surfactants with two identical and nonidentical hydrophobic chains. (Reprinted with permission from Ref. [203]. Copyright 2015 Royal Society of Chemistry Publications).

Figure 9

Simplified schematic representation of the physical structure of gemini surfactant: (a,b) are gemini surfactants with rigid and flexible spacers, (c,d) are gemini surfactants with short chain and long chain spacers, (e,f) are gemini surfactants with polar and nonpolar spacers, and (g,h) are gemini surfactants with two identical and nonidentical hydrophobic chains. (Reprinted with permission from Ref. [203]. Copyright 2015 Royal Society of Chemistry Publications).

Figure 10

Schematic route for preparing Laurus nobilis leaf extract powder that was used for mild steel corrosion prevention. (Reprinted with permission from Ref. [213]. Copyright 2020 Elsevier Publications).

Figure 11

Geometry of neutrally charged elemicin, eugenol, limonene, santamarine, spatulenol, and terpinyl acetate compounds found in Laurus nobilis leaf extract, the oxygen and carbon atoms chosen for protonation are indicated in blue. (Reprinted with permission from Ref. [213]. Copyright 2020 Elsevier Publications).

Figure 12

(a) FTIR spectra of the extract powder and the surficial film formed on the inhibited steel surface, (b) XRD patterns for the steel samples immersed in 1.0 M HCl solution in the presence and absence of PSLSE, (c) UV–Vis spectra before and after immersing the steel samples into 1.0 M HCl solution in the presence of PSLSE for 2.5 h. (Reprinted with permission from Ref. [215]. Copyright 2020 Elsevier Publications).

Figure 13

Structural groups of polymer inhibitors.

Figure 14

Scanning electron micrograph of poly(vinyl alcohol-cysteine). (Reprinted with permission from Ref. [231]. Copyright 2017 Arabian Journal of Chemistry Publications).

Figure 15

SEM images of mild steel surfaces after 24 h immersion in 1.0 M HCl solution in the presence of PDA-1, PDA-2, and PDA-3. (Reprinted with permission from Ref. [239]. Copyright 2020 Elsevier Publications).

Figure 16

SEM images of [TiO₂ NFs] (A,B) and [TiO₂ NFs/SBP] (C,D). (Reprinted with permission from Ref. [243]. Copyright 2013 Egyptian Journal of Petroleum Publications).

Figure 17

(a) Histogram of maximum inhibition efficiency values for six kinds of inhibitors, (b) box-whisker plots of maximum inhibition efficiency values for six kinds of inhibitors, the source of the data is in Supplementary Tables S2–S7.

Figure 18

Scatter plot of optimum concentration and the corresponding max inhibition efficiency for six kinds of inhibitors, and their respective the main region of the distribution (the source of the data is in Supplementary Tables S2–S7 where the optimum concentration values are given in moles/millimoles/micromoles per liter).

Figure 19

The number and the percentage of each type of inhibitor at the indicated range of temperatures that achieved the maximum inhibition efficiency. The source of the data is in Supplementary Tables S2–S7.