Two decades of research on green inhibition of steel corrosion: A bibliometric review

3.4.1. The ten most cited reviews

Table 2 presents a bibliometric analysis of several specialized scientific journals, mainly in the fields of electrochemistry, plants, and green corrosion inhibition. A set of indicators is provided, making it possible to assess both the scientific productivity, the impact and the quality of research in the scientific and academic community such as the number of papers published in 2024, reflecting the recent activity of the journal, the total number of citations, The h-index (or h-index), which measures both the quantity and quality of the journal’s publications and the SCImago Journal Rank (SJR) of 2024, A weighted indicator of academic influence [16].

Some journals are clearly distinguished by their influence and academic recognition. For example, “Colloids and Surfaces A: Physicochemical and Engineering Aspects,” “Journal of Molecular Liquids,” and “Scientific Reports” have particularly high indicators. These three journals, ranked in Q1, have h-indices of 205, 189, and 347, respectively, as well as SJR values greater than or equal to 0.92, testifying to a strong reputation and a specialized orientation in this field of research. By comparing the average number of citations per article, the journal “Scientific Reports” totals 292,548 citations for 13 articles, or about 22,500 citations per article, which indicates its leading position in this field, while “Pigment and Resin Technology” reaches 362 citations for 18 articles, or about 20 citations per article.

These figures show that the quality of the journal and its positioning in the quartiles (Q1 to Q4) strongly influence its academic impact. Journals classified as Q1, often published by large groups such as Elsevier, are systematically distinguished by better indicators (SJR, h-index, number of citations), reflecting their central role in the dissemination of scientific knowledge.

Table 2 highlights a marked diversity among scientific journals, both in terms of productivity and influence. Some journals, although very productive, remain less cited, while others, with a more modest volume of publications, manage to exert a very strong scientific impact. Thus, the qualitative ranking (Q1 to Q3), the h-index, and the SJR are essential criteria for evaluating the reputation and academic relevance of a journal.

3.4.2. The ten most cited articles

Carrying out a bibliometric study of published articles in the field of corrosion inhibition by plant extracts is a strategic approach to better understand the evolution, dynamics, and challenges of this rapidly expanding field of research. It makes it possible to identify and map the evolution of major scientific research trends, highlighting emerging topics such as extraction techniques, new ecological inhibitors or biopolymers, while assessing the progression of the number of publications and thematic evolution over time. In fact, the most cited articles often indicate significant advances in the understanding and assimilation of the principles of extractions, the most important part of the plant containing better inhibitors, as well as their physicochemical properties, and the methods with which they work. Such studies also highlight gaps in current research, such as the lack of long-term evaluations or insufficient work on specific industrial applications or environments [17]. By providing a clear mapping of existing knowledge, it effectively guides future work by avoiding redundancies and promoting innovation, particularly in the choice of thesis topics or scientific projects. Finally, since green corrosion is closely linked to environmental concerns and sustainable development, bibliometrics makes it possible to measure the evolution of this ecological awareness in the scientific literature, by evaluating the integration of concepts such as biodegradability, ecotoxicity, or green chemistry. In summary, far from being a simple count of articles, a bibliometric study on green corrosion is a real decision-making tool for any researcher wishing to be part of a relevant, current, and responsible scientific approach.

Table 3 [18-27] lists the most influential papers, ranked by citation in the field of corrosion inhibition, highlighting several key elements. At the top of the table is the most cited article “Corrosion inhibition by Justicia gendarussa plant extract,” published in 2009, with an impressive total of 716 citations. This strong recognition suggests that the study has made a significant contribution, either through the robustness of its experimental results or through an innovative approach in the use of natural inhibitors.

All these studies have shown that using plant extracts such as “Justicia gendarussa,” “Zenthoxylum alatum,” and “Phyllanthus amarus” in the first (716 citations), second (533 citations), and third article (506 citations) successively, and the plant extracts “Chamaemelum mixtum L.,” “Cymbopogon proximus,” “Nigella sativa L.,” and “ (Nigella sativa L. In the fourth study (484 citations), the effectiveness of inhibiting the corrosion of steel in corrosive environments such as hydrochloric acid and sulfuric acid increases with increasing concentrations, giving it the ability to be good biodegradable inhibitors for corrosion.

In addition, the majority of the most cited articles were published between 2009 and 2018. This temporal concentration indicates a particularly dynamic period for research on green inhibitors, probably stimulated by the rise of issues related to sustainable development in chemistry at that time.

The majority of the articles appeared in the journal Corrosion Science, a very high-level journal, classified as Q1. This editorial choice testifies to the importance of this journal in the dissemination of major scientific advances on green corrosion. It thus plays a central role as a reference platform for researchers in the field.

Such studies enrich the academic scientific field and often guide practical applications and policy formulations in the areas of prevention against the phenomenon of corrosion of materials.

Such an analysis also helps to identify the main players in the field, whether they are influential researchers, pioneering institutions, or countries particularly invested in this issue (such as India, China, or Iran).

In terms of scientific impact, bibliometrics makes it possible to rank the most recognized journals (especially those of Q1 rank with a high h-index), which is a valuable benchmark for choosing the best sources of publication or collaboration.

Finally, some names frequently come up among the authors of these publications, such as Okafor, Satapathy, or Abdel-Gaber. Their repeated presence reveals their status as influential figures, even pioneers in this field of research. These researchers are valuable sources for effective scientific monitoring and can represent strategic partners for possible future collaborations.

3.5.1. Most relevant authors

The bibliometric analysis of authors is a valuable tool for better understanding the structure, dynamics, and main actors of a scientific field [28]. Applied to the field of green corrosion, it offers several intriguing perspectives. Such a study makes it possible to identify the most influential researchers. By analyzing both the quantity (number of publications) and the quality (index h, number of citations) of their contributions, it becomes possible to identify pioneering scientists on an international scale. It also makes it easier to identify potential collaborators or experts to be solicited for research projects. Such an analysis makes it possible to map scientific production. By cross-referencing bibliometric data with the countries of affiliation, we can distinguish the most dynamic regions of the world in the field, such as Morocco, Iran, or China, and better understand the geographical distribution of research efforts, particularly on themes with an ecological scope.

The bibliometric study also helps to assess the impact and recognition of researchers. Indicators such as the number of citations and the h-index give a clear idea of the real scientific significance of the work, as well as its visibility on the international scene.

In addition, this analysis makes it possible to appreciate the dynamics of scientific collaboration. The rate of international co-publication is an indicator of the degree of openness of researchers to cooperation. It also reflects their ability to be part of multidisciplinary projects on a global scale, often a guarantee of quality work.

Finally, this approach helps to guide future research. By highlighting the most prolific and cited authors, it facilitates the identification of reference publications while guiding strategic choices in terms of collaboration, funding, and dissemination of scientific results.

The bibliometric analysis of authors who have contributed to research on green corrosion highlights several significant trends, both in terms of scientific productivity and international impact and collaboration.

The results of this analysis are shown in Table 4, which shows that some researchers stand out for their high number of publications in the field. This is the case of Ramezanzadeh B (38 articles), Hammouti B (35 articles), and LI X (27 articles), who appear to be major figures in this field of research. Their sustained involvement testifies to a long-term scientific commitment to themes related to ecological corrosion.

For scientific impact, measured by the h-index and the total number of citations, Ramezanzadeh B and Hammouti B also occupy leading positions. The former has an h-index of 96 and a total of 12,817 citations, while the latter has an h-index of 91 and a remarkable total of 12,538 citations. These figures reflect a strong recognition of their work by the international scientific community. Zarrouk A, also very active, has similar indicators (h-index of 88, 8181 citations), which reinforces the importance of his contribution.

The geographical analysis reveals a predominance of authors from Iran, Morocco, and China, which underlines the dynamism of these countries in research on green corrosion. Morocco stands out not only for the productivity of its researchers (such as Hammouti B., Zarrouk A., and Salghi R.), but also for their strong integration into international collaboration networks, marked by cooperation rates on a global scale reaching 68.7%, 69.6%, and 86.7%, respectively. that illustrate their significant impact on the global scientific community. In contrast, some Iranian authors, although very productive, exhibit lower collaboration rates (around 10%), which may limit the international dissemination of their work. The study also highlights some notable contrasts: a high number of publications is not always accompanied by a proportional bibliometric impact. For example, Li X, while active in the field, has a more modest h-index and a relatively low collaboration rate, which could indicate more localized visibility of his research.

Haldhar R’s contribution in this field, with 16 papers out of a total of 185, as well as a somewhat modest h-index of 34 and 2346 citations, is remarkable as a good collaborator at the international level, with a percentage of 72%, which reflects his active engagement in global research initiatives.

In short, this analysis reveals varied profiles among researchers: some combine productivity, scientific visibility, and international cooperation, while others are characterized by sustained production but are more focused on a national context. These results can guide future choices in terms of collaboration, funding, and scientific valorization.

3.5.2. Pioneering countries

Carrying out a bibliometric study by country in each scientific field is of major interest in understanding the dynamics of information and knowledge on a global scale. Based on quantitative indicators, such a study not only makes it possible to identify the most contributing and influential countries, but also to map the networks of collaboration and exchange between nations [29].

Table 5 presents a comparative analysis of the scientific output of ten countries, based on several key indicators such as the number of publications, total citations, average citations per article, and collaborative links. This analysis highlights a notable diversity between countries in terms of scientific production, intensity of collaboration, and impact measured by citations. India stands out clearly with 284 published papers and 8,103 citations, which testifies to a strong research activity in the field of corrosion inhibition by plant extracts. It is also highly connected, with 15 collaboration links and a high total link strength (96), which reflects a good anchoring in international networks. It is followed by Nigeria and China, each with 113 publications. However, China is ahead of Nigeria in terms of total citations (3836 vs. 2723), reflecting a stronger scientific impact.

Arab and African countries such as Morocco, Saudi Arabia, and Egypt also display significant scientific activity. Morocco (106 documents) and Saudi Arabia (92 documents) obtain a similar total of citations (around 2,850), revealing a good recognition in the scientific community. Egypt, although slightly less productive (62 papers), has a high average of citations per article (40.26), reflecting the quality or impact of its publications. South Africa, with only 44 publications, stands out with a remarkable average of 47.55 citations per article, making it one of the best-performing countries qualitatively.

Iran, despite a relatively limited number of publications (64), has the highest average score of citations per article (60.33), highlighting a high visibility or notable quality of its work. Conversely, Malaysia has the lowest average (15.85), suggesting a more limited impact of its searches.

In terms of scientific collaboration, India, Morocco, and Saudi Arabia have a high number of links (15) and a high intensity of collaboration (Total Link Strength ranging from 96 to 119). This strong integration into international networks seems to contribute to a better dissemination and recognition of their work. On the other hand, other countries such as Iran and Algeria have a smaller network of collaboration, which could hinder their scientific influence.

In conclusion, this study highlights the diversity of scientific dynamics in different countries. India stands out for its productivity, while Iran and South Africa stand out for the quality and average impact of their publications. Arab countries are showing a growing presence in the international scientific landscape, driven by increasingly marked collaborative efforts.

Finally, these analyses have an important strategic dimension. They provide decision-makers with objective elements to guide research policies, support centers of excellence, fill any gaps, or encourage effective international cooperation. This type of study thus contributes to positioning a country in the global scientific landscape and strengthening its competitiveness.

Figure 3 illustrates the scientific collaboration between different countries through a bibliometric network. Each node represents a country, while the lines connecting these nodes indicate co-publication links between researchers from those countries. The size of the circle reflects the importance of the country in the network, i.e., the number of publications and interactions that the nation makes with others, the thickness of the lines between the nodes indicates the strength of the collaborative links, and the colors indicate regional or thematic collaboration groups, called clusters.

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Figure 3.

Network visualization map of inter-country collaboration.

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At the center of the network, we can see that India occupies a strategic and dominant position. Her circle is the largest, which shows that she is both highly productive scientifically and very active in international collaboration. India is building strong ties with countries in Asia (such as South Korea and Nepal), Western countries (the United States), as well as North Africa and other regions, which is a testament to its role as a global scientific intersection.

The red group includes countries such as Nigeria, China, Iran, Malaysia, Indonesia, and South Africa. This group illustrates a strong South-South collaboration, particularly between countries in Africa and Asia. The links are numerous and dense, revealing dynamic scientific exchanges within this group.

The blue group, on the other hand, brings together countries from the Maghreb and the Middle East: Morocco, Algeria, Tunisia, Egypt, Saudi Arabia, and Turkey. There are marked regional interactions, showing a growing desire for scientific cooperation between Arab and Mediterranean countries.

Finally, the Green Group is organized around India and includes South Korea, the United States, Nepal, and Romania. It represents an opening to East Asia, North America, and Eastern Europe, suggesting a geographical diversification of scientific partnerships.

In conclusion, this map highlights a dynamic geography of international research, where countries such as India, Morocco, and China play a leading role in building bridges between different regions of the world. It also reveals the importance of regional cooperation, while stressing the need to strengthen interconnection to promote scientific research in the field of corrosion inhibition.

Figure 4 illustrates the global distribution of scientific output, i.e., the volume of academic publications from each country. Carried out using the bibliometric tool Bibliometrix, this visualization is based on data extracted from the international database Scopus. Countries are represented by shades of blue: the darker the color, the greater the country’s scientific contribution; conversely, lighter shades indicate moderate production, while grey areas indicate no or very little scientific activity in this field. The analysis of this map reveals that countries such as India, Morocco, China, Iran, and Turkey are distinguished by a particularly high scientific production. This reflects a growing commitment to scientific research and development in various fields, including corrosion inhibition. Other countries such as the United States, Mexico, Brazil, France, Germany, and Spain also show sustained activity, although with varying intensity depending on the region. Africa, although unevenly represented, is showing encouraging signs, particularly in the Maghreb with a very active Morocco, as well as in Egypt, Nigeria, and South Africa, where scientific research is beginning to gain momentum despite persistent structural challenges. On the other hand, some areas, particularly in Central Africa, Central Asia, or certain island regions, appear to be lagging, which can be explained by limited access to resources, funding, or research infrastructures. This map offers a clear overview of the global geography of science. It makes it possible to identify the most dynamic countries, to highlight areas of scientific development, and to identify regions where efforts still need to be made. It is thus a strategic tool to guide research policies, foster international partnerships and strengthen scientific equity on a global scale.

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Figure 4.

Country scientific production.

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3.5.3. Keywords mapping

Bibliometric analysis of keywords allows us to understand the structure and evolution of a scientific field [30]. By identifying the most frequent terms, it highlights major themes, such as metal corrosion or green inhibitors, and detects emerging axes. It also reveals the links between concepts and disciplines, thanks to the connections between keywords [31]. Grouping into clusters helps visualize the organization of the field of study. This method is therefore a strategic tool for directing research towards innovative subjects.

Table 6 presents the main keywords used in a set of scientific publications on corrosion, in particular, metal corrosion and prevention methods. Each keyword is accompanied by several indicators that make it possible to assess its place and influence in the scientific network.

Among the most frequent terms is “corrosion inhibitors,” which appears 409 times and has 223 links with other keywords, making it one of the most central terms in the field. It is closely associated with “steel corrosion” (375 occurrences, 222 links) and “corrosion” (398 occurrences, 222 links), indicating that steel is a reference material in corrosion-related research, and that prevention by inhibitors is a scientific priority.

The keyword “electrochemical corrosion” (250 occurrences) highlights the importance of electrochemical approaches in the study of corrosion phenomena. Similarly, “adsorption” (287 occurrences) highlights that the mechanisms of interaction between inhibitors and metal surfaces are frequently studied.

The “Total Link Strength” indicator, which measures the overall strength of relationships between keywords, confirms the central role of the previous concepts. For example, “corrosion inhibitors” has a total bond strength of 5,972, reflecting a strong integration into the scientific network of the field.

The “clusters” indicate a structuring of the field into sub-domains: each group of keywords brings together similar concepts, suggesting specific research axes (materials, electrochemical techniques, green approaches, etc.).

This analysis shows that corrosion research focuses on the protection of metals, in particular steel, using inhibitors, and that electrochemical methods and adsorption mechanisms are cross-cutting themes strongly represented in the literature.

Figure 5 represents a bibliometric map generated by the VOS viewer software, constructed from keywords extracted from a set of scientific publications from 2004 to 2025. This map allows you to visualize the semantic and scientific relationships between the most frequent themes in the field of corrosion, that related to green inhibitors or those from natural sources. The map is based on a method of co-occurrence of keywords. The terms are represented as colored nodes. The terms of the same colors form a grouping called a “cluster,” each distinguishing an axis of interest in research in the field of corrosion.

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Figure 5.

Keywords: Co-occurrence network visualization map.

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The following provides a detailed description of each group on the map.

Group 1 (Red): This group is in the center of the map, and it is focused on surface analysis techniques; the main keywords are “electrochemical corrosion scanning” and “electron microscopy.” This cluster brings together advanced physicochemical studies on metal surfaces. Spectroscopy-related terms (Fourier transform infrared-FTIR, UV-Vis, energy dispersive X-ray-EDX) and electron microscopy (scanning electron microscopy-SEM, field emission scanning electron microscopy-FESEM) suggest methods used to characterize the interaction of inhibitors with metal. It also deals with molecular modeling to understand the behavior of inhibitors at the atomic level.

Group 2 (Blue): This group includes terms such as “steel corrosion,” “corrosion inhibitors,” and “plant extracts,” reflecting the interest of ecological inhibitors from plant sources. We explore their effectiveness in various environments, such as NaCl (salt water), acidic environments, or materials such as reinforced concrete. The presence of words such as “sustainable development” and “environmental protection” shows an ecological and sustainable orientation of research.

Group 3 (Green): This group includes the key words: “plant extract,” “corrosion,” “steel,” and “polarization.” This cluster addresses the experimental and thermodynamic aspects of corrosion. The study of parameters such as enthalpy, temperature, acidity, current density, etc., aims to quantify the effectiveness of inhibitors. The appearance of the word “nonhuman” may indicate that some research is evaluating toxicity or environmental impact on non-human models.

Group 4 (Yellow): This group contains terms such as “adsorption,” “mild steel,” and “activation energy.” This cluster deals with the adsorption of inhibitors on mild steel and the quantification of this adsorption via isotherms (Langmuir, Freundlich). The notions of lost weight, Tafel’s blocks, and activation energy are classic tools for evaluating the efficacy of inhibitors in acidic media (HCl, H₂SO₄). We also note the use of natural compounds such as essential oils.

Group 5 (Purple): This small cluster focuses on analytical methodologies employed in corrosion studies. It includes electrochemical methods, mass loss measurements, and analysis tools such as scanning electron microscopy (SEM) to observe surfaces. This shows that the optimization of experimental protocols is an area of research.

The co-occurrence map shows a clear structuring of the field of research around the corrosion of metals, particularly mild steel, and natural solutions to inhibit this corrosion. The analysis reveals five main areas:

• 1.

  Molecular mechanisms of adsorption.

• 2.

  The effectiveness of plant extracts as inhibitors.

• 3.

  Chemical and physical characterization methods.

• 4.

  Thermodynamic and experimental effects.

• 5.

  Environmental concern in the development of sustainable alternatives.

This mapping thus offers a synthetic but detailed view of the major research orientations in the field of green corrosion inhibitors.