A Comprehensive Comparative Review of Corrosion Behavior, Mechanisms, and Protection Strategies for Metallic Materials in Marine Environments

Ali Fadiel AF and Elmnifi M

Published on: 2025-12-31

Abstract

The problem of corrosion under marine conditions is still a primary concern faced by engineering materials subjected to exposure to the sea, where high chloride levels, varying temperatures, mechanical stress, and microbial presence all contribute to the rate of corrosion. This paper presents an in-depth literature review of 19 recent publications between 2020 and 2025 that address corrosion behavior, prevailing mechanisms, methods of assessment, and corrosion prevention strategies of steels, stainless steels, duplex alloys, aluminum alloys, and copper-based materials. Systematic literature identification, screening, data extraction, and thematic comparisons were employed as structured methodologies.

The results indicate that there are definite performance differences between materials, with carbon steels having the highest, whereas austenitic stainless steels, though less resistant, are still prone to pitting, crevice corrosion, and stress corrosion, particularly at high temperatures or high levels of sulfide. Duplex stainless steel S32205 has a high level of corrosion resistance; the corrosion rate is much lower than that of mild steel, and passive films in seawater are highly stable. Localized intensification of corrosion was observed in the welded locations of the aluminum alloys, and Ni- and Ni-Cr-based coats are of significant benefit in copper alloys.

In all investigations, localized corrosion (pitting) was the most common, followed by microbiologically controlled corrosion (MIC), corrosion fatigue, and SCC in combined mechanical and chloride corrosion environments. Potentiometric polarization and Electrochemical impedance spectroscopy 20(EIS) are electrochemical techniques that were found to be the most useful in assessing the behavior of corrosion and the performance of any coating using SEM and XRD analysis. Protection measures such as high-technological coating, cathodic protection, and optimized alloy selection were observed to accelerate durability under austere conditions in the sea.

In general, this synthesis highlights the importance of a comprehensive approach to corrosion management, including material selection, surface engineering, cathodic protection, and continuous control, to guarantee the high stability of marine structures. Key gaps in the research are also identified in the study, leading to the conclusion that further research on real-time monitoring technologies and long-term behavior of emerging alloy systems in variable seawater is necessary.

Keywords

Seawater exposure testing; Corrosion mitigation strategies; Integrated corrosion management; Offshore structures; Surface modification

Methodology

The review methodology used in this study is structured to systematically identify, select, and synthesize recent research on corrosion behavior and protection strategies in marine environments. An extensive literature search was performed targeting publications published between 2020 and 2025 in major scientific databases, such as ScienceDirect, SpringerLink, Wiley Online Library, MDPI, SAGE Journals, and ResearchGate. Keywords such as marine corrosion, seawater corrosion, corrosion resistance, pitting corrosion, stress corrosion cracking, corrosion fatigue, MIC, protective coating, and cathodic protection were also used to ensure wide and important coverage.

Predetermined inclusion and exclusion criteria were used to screen the initial pool of studies included. The studies considered only those that researched corrosion in seawater or coastal marine environments and involved materials frequently used in marine environments, such as carbon steel, stainless steel, duplex stainless steel, aluminum alloys, and copper-based alloys. Articles that were too brief in terms of experimental description, articles not relevant to corrosion, and articles without full texts were filtered out. Following the screening process, 19 studies were selected for an in-depth review. [1,3,4,6]

Each selected study was subjected to a systematic data extraction process to maintain consistency and comparability. The information extracted included the year of the study, type of material used, environment, methods of the experiment (e.g., EIS, potentiodynamic polarization, weight-loss tests, SEM, fatigue testing), corrosion mechanisms investigated in this study, and important corrosion behavior and protection performance findings. This enabled the methodical grouping and appraisal of various experimental methodologies and findings presented in the literature.

Thematic and comparative analyses were used to extract data for the synthesis. Research papers were analyzed in groups to establish patterns of common corrosion, material peculiarities, and variations in the functioning of different environments. Additionally, the efficacy of the reported protection methods, including coating, inhibitors, cathodic protection, and alloy choice, was assessed, and the emerging technologies and gaps in knowledge that require additional research were determined. [2,5,8]

This combined approach would ensure that the review offers holistic, balanced, and scientifically sound knowledge of the current discoveries in marine corrosion studies to make wise decisions regarding the choice of materials and the design of protective systems to be used in harsh marine conditions.

Figure 1: Workflow of the systematic literature review methodology adopted in this study, including literature search, screening and selection, data extraction, thematic classification, comparative analysis, and synthesis.

Problem Statement

Materials exposed to marine environments are subject to daunting environments with high chloride concentrations, changing temperatures, stress, and biological activity. These factors enhance the corrosion rate, structural degradation, shorten service life, and increase maintenance costs. Although extensive studies have been conducted on corrosion mechanisms and protection methods, the available results are widely dispersed across different studies, using different methods, and differ in relation to materials, environmental factors, and testing procedures.

A generalized comparative analysis of recent scientific research is necessary to establish the existing corrosion mechanisms, the appropriateness of various metals and alloys when used in the marine environment, and the protection measures that are the most reliable when used either in situ or in simulated seawater conditions. In the absence of such a synthesis, engineers and researchers have had difficulties choosing the best materials, developing robust systems, and adopting pragmatic corrosion reduction strategies in the sea [7-9].

Objectives

This study aims, first of all, to review and analyze recent studies (2020-2025) on the topic of corrosion behavior and protection measures under marine environments. To achieve this, the research has the following specific objectives:

Determine and outline the latest scientific research analyzing corrosion processes and degradation of materials in seawater and coastal marines.

The corrosion characteristics of significant engineering materials, such as carbon steels, stainless steels, duplex alloys, aluminum alloys, and copper-based alloys, in different marine environments.

Examine experimental methodologies (e.g., EIS, potentiodynamic polarization, SEM, weight-loss tests, and fatigue analysis) to assess corrosion in the selected literature.

Compare and contrast corrosion processes such as uniformity, pitting, crevice, stress corrosion cracking (SCC), corrosion fatigue, and microbiologically induced corrosion (MIC).

The effectiveness of the protection strategies used to reduce marine corrosion includes coatings, cathodic protection, inhibitors, and alloy modifications.

Defining gaps in research and new trends to determine future research on marine corrosion and material selection.

Offers practical suggestions on how engineers and designers may choose the right material and install sound corrosion-resistant mechanisms in the sea.

Research Significance

This research is important because it summarizes and contrasts the results of 20 recent, high-quality research studies on marine corrosion and forms a single, convenient basis for learning degradation dynamics and protection methods. By combining findings on various materials, environments, and corrosion processes, this study provides engineers, researchers, and decision-makers with a better understanding of the materials and protection systems used when exposed to the marine environment.

This review also provides valuable information for evidence-based material selection to support offshore platforms, pipelines, desalination plants, and coastal infrastructure, where reliability and durability are crucial. The strengths and limitations of the alloys commonly used include carbon steels, stainless steels, duplex steels, aluminum alloys, and copper-based materials. By identifying these strengths and limitations, this study allows for the optimization of design selection and long-term maintenance plans.

Moreover, by introducing new processes and mechanisms, including MIC and corrosion fatigue, and assessing the performance of the various corrosion control measures employed, including the use of coatings, cathodic protection measures, and the use of alloy additions, this study promotes the use of combined corrosion control measures instead of isolated methods. By establishing methodological inconsistencies and areas necessary for further exploration in the future, this study also provides the basis for future research, especially under the conditions of real-life exposure and long-term observation.

The importance of this study lies in the fact that it can convert unconnected corrosion research into a comparative and coherent framework that can enhance scientific knowledge and directly introduce new, robust, and cost-effective marine engineering solutions.

Literature Gap

Despite the large amount of research conducted to understand corrosion behavior in marine environments, several gaps remain in the existing body of knowledge. First, the literature tends to concentrate on individual materials in a controlled laboratory environment, whereby the extrapolation of the findings is constrained and probably does not represent the richness of real ocean water, especially in terms of temperature variation, oxygen gradients, and biofouling influences. Second, consensus on assessment procedures among corrosion investigations is lacking; variability in exposure durations, electrochemical procedures, and simulated seawater composition results in discrepancies that complicate direct comparisons of materials.

Furthermore, localized corrosion processes have been studied in isolation (pitting, stress corrosion cracking, and microbiologically influenced corrosion MIC). However, few studies have combined these processes into an overall picture that incorporates the combined chemical-mechanical-biological processes characteristic of marine structures. In addition, studies on protective measures tend to cover only in isolation, which are referred to as coatings, cathodic protection, or even the use of alloy enhancements, but do not comment on the possibility of having a hybrid or multilayered system that could provide better life expectancy of the material. Finally, there has been a lack of focus on new materials (e.g., the development of higher-grade duplex or surface-enhanced alloys) and the performance of protective systems over time in less steady (varying) or less cyclic environmental conditions.

These loopholes emphasize the necessity of an overall, comparative synthesis of recent studies to create more definite performance patterns, material-specific weaknesses, and strategies to prove their practical effectiveness in severe sea conditions.

Marine corrosion behavior, mechanisms, and protection strategies: A comprehensive comparative review across the Metallic Materials (2020-2025): Analysis of 19 Recent Research.

	Study / Reference (Year)	Material / Environment / System Type	Content / What the Study Focused On	Results / Key Findings
1	2025 — Assessment of Corrosion in Naval Steels Submerged in Seawater	Naval Steel immersed in natural & artificial seawater	Corrosion progression of DH36 naval steel via EIS, weight-loss, SEM, magnetic permeability mapping under marine immersion	Identified rapid initial corrosion with lepidocrocite/goethite formation; corrosion rate slows as product layer densifies; magnetic measurements correlate well with corrosion layer growth — useful for non-destructive condition monitoring. [10]
2	2025 — Smart material design via accelerated corrosion evaluation	Marine / Seawater exposure (accelerated testing)	Review of high-throughput corrosion testing & characterization integrated with multi-factor measurements + AI for material design.	Proposes a framework for rapid evaluation of corrosion resistance, enabling the design of corrosion-resistant materials for marine environments. [11 ]
3	2025 — Enhancing corrosive?wear resistance of 316 austenitic stainless steel in seawater by titanium infiltration	316 SS in seawater (coated/treated)	Surface modification of 316 SS via titanium-infiltration (plasma/thermal treatment), then corrosion + wear tests in seawater	Treated 316 SS shows significantly improved corrosion and wear resistance compared to untreated 316 SS — a viable protection strategy for seawater service. [12]
4	2025 — Elucidating stress corrosion cracking mechanisms in 316L stainless steel in marine environments	316L SS submerged in a marine environment (stress + corrosion)	Investigating stress?corrosion cracking (SCC) behavior of 316L in marine conditions under stress + salt exposure	Provides insight into crack initiation and propagation mechanisms under combined mechanical stress and chloride corrosion — relevant for structural integrity design in seawater. [13]
5	2020 — Corrosion Behavior of AISI 1045 Steel in Seawater	Plain/mild carbon steel in seawater	Corrosion behavior of AISI 1045 alloy under seawater immersion — electrochemical and weight-loss analysis	Demonstrates a comparatively high corrosion rate in seawater, indicating that non-alloyed steel is poorly suited for long-term seawater exposure without protection. [14]
6	2021 — Corrosion and Protection of Steels in Marine Environments: State-of-the-Art and Emerging Research Trends	Marine / Coastal Environments	Collection of studies & reviews summarizing corrosion behavior of various steels in seawater + protective strategies (coatings, alloys, maintenance)	Provides a broad overview of corrosion mechanisms, protective measures, and guidelines — helpful background when selecting material or designing protection. [15]
7	~2020 — A Review on Corrosion Fatigue and Its Related Testing Methodologies	Corrosive / Saline Environments + Mechanical Loading	Review summarizing methods for assessing corrosion-fatigue interactions in metals exposed to corrosive/saline conditions under cyclic loading	Highlights the importance of combining corrosion and fatigue tests; defines protocols and pitfalls — functional if research involves mechanical stress + seawater exposure.[16]
8	2024 — Study on seawater corrosion resistance of copper alloy	Copper-based alloys immersed in seawater (with/without coatings)	Evaluation of corrosion behavior of copper/alloys + effect of protective coatings (e.g., Ni, Ni-Cr, Ni-Cr-Fe) in seawater	Showed that specific coatings significantly reduce corrosion rate vs bare copper, making copper alloys potentially usable if properly protected.[17]
9	2025 — Advancements in corrosion studies and protective measures for copper and copper-based alloys in varied environmental conditions	Copper & copper?based alloys in saline/marine / variable environments	Review of recent developments in corrosion resistance, coatings, inhibitors, and design guidance for copper-based materials under marine/harsh conditions	Summarizes effective protection strategies, failure modes and selection criteria — helpful reference for design of copper-based seawater systems. [18]
10	2023 — Corrosion Behavior of Stainless Steel in Seawater in the Presence of Sulfide	Stainless steel (AISI 304L & 316L) in seawater with sulfide ions	Electrochemical and weight-loss measurements to study the effect of temperature and sulfide concentration on corrosion behavior	Increased pitting corrosion with higher temperature and sulfide concentration; 316L showed better resistance compared to 304L. [19]
11	2022 — Corrosion in marine and offshore steel structures: Classification and overview	Marine / Offshore steel structures in various environments	Comprehensive review of corrosion mechanisms and protection strategies for marine and offshore steel structures	Highlights the multiple types of corrosion (uniform, pitting, crevice, MIC) and protection methods, including cathodic protection and coatings. [20]
12	2023 — Seawater Corrosion Resistance of Duplex Stainless Steel and the Axial Compressive Stiffness of Its Reinforced Concrete Columns	Duplex stainless steel (S32205) in seawater	Comparing the corrosion behavior of S32205 and mild steel (HRB400) in seawater environments — evaluation of rebar performance	S32205 showed a corrosion rate 1/15 that of mild steel — excellent resistance to chloride-induced corrosion and stable passive layer formation. [21]
13	2025 — A review on the environment’s influence on coastal marine steel corrosion and in-situ monitoring	Steel in coastal marine environments	Review of environmental factors (salinity, temperature, biofouling) on corrosion behavior of steel, with field monitoring techniques	Emphasizes the importance of regular monitoring and environmental assessments to mitigate corrosion, especially in coastal areas. [22]
14	2023 — Microbially Influenced Corrosion of Steel in Marine Environments (MIC Review)	Steel in marine environments with biological activity (biofilms)	Focuses on the role of microorganisms in accelerating corrosion processes, particularly pitting corrosion in steel	Biofilm formation exacerbates corrosion; microbial activity can alter the protective oxide layer, leading to localized damage. [23]
15	2022 — Corrosion Fatigue of 17?4PH Stainless Steel in Simulated Seawater	17-4PH Stainless Steel in seawater + cyclic loading	Fatigue and corrosion interaction studies (S?N curves), with emphasis on pitting and stress corrosion cracking under seawater exposure	The fatigue limit in seawater was approximately 40% lower than in air due to the combined effects of corrosion and mechanical loading. [24]
16	2024 — Study on Corrosion Fatigue Behavior of 304L Austenite Stainless Steel in 325 °C High-Temperature Water Environment	304L SS in high-temperature, high-pressure seawater environments	Investigates fatigue crack growth under simulated seawater conditions with dissolved oxygen and temperature changes	Increased fatigue crack growth under high temperature and pressure, with a significant effect of dissolved oxygen on the corrosion rate. [25]
17	2023 — Localized Corrosion of High-Grade Stainless Steels: Grade Selection in Chlorinated Seawater	High-grade Stainless Steel in natural seawater	Localized corrosion, including pitting and crevice corrosion, on high-grade stainless steels in seawater conditions	High-grade stainless steels are still vulnerable to localized corrosion, especially in biofilm-laden seawater, despite their initial resistance. [26]
18	2020 — Corrosion of Carbon Steel in Marine Environments: Role of Corrosion Product Layers	Carbon steel in seawater	Study of corrosion product layers formed during carbon steel exposure in seawater, focusing on the effects of biofouling and oxygen depletion.	Corrosion product layers thickened over time; the inner layers were anaerobic, and biofouling obstructed oxygen diffusion, thereby impacting corrosion behavior. [27]
19	2025 — Corrosion Control and Its Application in Marine Environments (Review)	Various materials in marine environments	Review of various corrosion control methods for marine environments, including coatings, cathodic protection, and design practices	Offers practical guidance for selecting corrosion protection strategies based on material type and environmental conditions (seawater, splash zones, submerged). [28]

Results and Discussion

This section is a synthesis of the results of 19 current studies on marine corrosion, including steels, stainless steels, duplex alloys, aluminum, and copper-based alloys that are in contact with seawater and coastal conditions. The discussion covers the results in the form of (i) material behavior, (ii) predominant corrosion mechanism, (iii) evaluation techniques, and (iv) the efficacy of protection strategies and an overall interpretation of the results for marine engineering applications.

Behavior of Various Materials to Seawater Corrosion

The literature confirms that carbon and mild steels have the highest rates of corrosion in seawater. The AISI 1045 steel work was also found to exhibit a fast rate of mass loss and corrosion current density, which suggests that unalloyed steels cannot be immersed without any protection. Although the corrosion products are formed quite quickly, they do not create a stable coating, and localized corrosion is formed over time.

Conversely, austenitic stainless steels (304 L and 316 L) are much more resistant because of the presence of chromium and molybdenum, which favors the development of a passive film. Nevertheless, several studies have indicated that this passive layer is susceptible to failure in environments containing a large amount of chloride, which causes pitting and crevice corrosion. Sulfide ions and high temperatures had a significant effect on increasing pitting susceptibility, and 316 L was significantly better than 304 L because it contained more Mo.

The duplex stainless steel S32205 demonstrated the most positive behavior among the examined steels. Comparative tests of rebar in seawater have proved that its corrosion rate is approximately one-fifth of that in mild steel because of the more stable passive layer and the increased resistance to attack by chlorides. These findings justify the increasing use of duplex grades in highly hostile marine environments.

In the case of aluminum alloys, the results of friction-stir-welded AA5086 show that both the heat-affected and thermo-mechanically affected regions are more vulnerable to localized corrosion than the base alloy. The microstructural heterogeneity brought about by welding facilitates the initiation of pits, which may undermine structural integrity during marine service.

Copper and copper alloys exhibit moderate natural resistance, yet are highly reliant on the condition of the surface. Experiments on coated copper alloys have shown that Ni- and Ni-Cr-based layers can significantly lower the rate of corrosion compared with bare copper, implying that copper may also be a feasible choice in seawater systems when used with a suitable protective coating.

Preeminent Corrosion Mechanisms

In materials, localized corrosion has been found to be the most essential mode of damage. Stainless steel, duplex grades, aluminum welds, and copper alloys were repeatedly tested and found to exhibit pitting and crevice corrosion. The penetration of the passive film by chloride ions forms metastable pits that may extend to deep cavities and do not typically show any macroscopic evidence until the wall thickness has been severely depleted.

Several studies have outlined stress-corrosion cracking (SCC) in 316 L stainless steel under a combined tensile stress and chloride atmosphere. Frequently, pit sites or microstructural heterogeneities develop cracks and propagate along particular crystallographic orientations, which has heightened the need to regulate residual marine structure stresses and loads.

Microbiologically controlled corrosion (MIC) has also been found to be a significant factor in the acceleration of steels in natural seawater. The sulfate-reducing and other bacteria biofilm formation changes the local electrochemistry, which enhances under-deposit and pitting corrosion and changes the makeup of corrosion products.

In addition, 17-4PH and 304 L stainless steels have been reported to exhibit corrosion fatigue under cyclic loading in seawater. The fatigue limit under corrosive conditions was reduced to up to 40 per cent of the limit in air, with the base and surface flaws being favorable locations for crack initiation. This observation is particularly applicable to elements that are subjected to waves, vibrations, or rotating forces.

Table 2: Quantitative meta-synthesis of the dominant corrosion mechanisms reported across the 19 reviewed studies (2020-2025).

Corrosion mechanism	Number of studies (≈)	Share of sample (≈)
Corrosion fatigue	3	~16%
Microbiologically influenced corrosion	2	~11%
Localized corrosion (pitting/crevice)	2-3	~10-15%
Stress corrosion cracking (SCC)	1-3	~5-15%
Uniform corrosion/product layers	2	~11%

According to this quantitative meta-synthesis, the most common types of degradation processes explored in the literature reviewed are corrosion fatigue and localized corrosion mechanisms (pitting and crevice corrosion), which have a vexing effect on the integrity of metallic components in seawater over the long term. The conspicuous appearance of microbiologically controlled corrosion (MIC) emphasizes the increased awareness of biological activity as a significant accelerator, especially in steels in natural seawater. Although the research did not present explicit solutions to stress corrosion cracking (SCC), its presence in several materials, particularly austenitic stainless steel, supports its applicability under conditions where tensile loads and chloride environments are combined. The development of layers of corrosion products and uniform corrosion was also studied in a number of studies, as it was pointed out that general and localized attack should be made clear. Together, these tendencies prove that the study of marine corrosion is becoming more concerned with the correlation between mechanical, electrochemical, and biological components instead of individual processes.

Assessment Methods and their revelations

All research papers utilized electrochemical, gravimetric, and microstructural procedures. Potentiodynamic polarization was used to provide data on the corrosion potential, corrosion current density, and pitting potential to make a quantitative comparison of the alloy performance. Electrochemical impedance spectroscopy (EIS) is particularly useful for evaluating the robustness of a coating and passive film properties because it records the charge-transfer resistance and capacitive behavior with time.

Conventional weight-loss measurements were still useful in determining long-term average corrosion rates, but were not in a position to determine the local mechanisms. SEM and XRD analyses helped to characterize the corrosion morphologies and products in detail and therefore differentiated between uniform attack, pitting, MIC, and SCC. Experiments involving the integration of electrochemical measurements with microstructural analysis provided the most detailed insight into the corrosion behavior.

The effectiveness of the corrosion protection strategies was analyzed in terms of the 5.4th.

Throughout the review, several protection strategies were considered. Surface modification and coating were found to have definite merits: titanium infiltration of 316 stainless steel enhanced the wear resistance and corrosion. On the other hand, Ni and Ni-Cr finishes on copper alloys greatly decrease both general and localized corrosion. These treatments stabilize the passive films and reduce the number of active defect sites.

The use of cathodic protection (CP) with sacrificial anodes or impressed current is still a cornerstone initiative for carbon steel and offshore structures. Review papers established that CP can inhibit corrosion currents and reduce pitting in submerged and splash-zone areas, particularly when used together with coatings to effectively suppress corrosion currents.

The choice of alloy is, in itself, a strategic protection measure. The superior performance of duplex stainless steels compared to mild and conventional stainless steels in chloride-bearing environments indicates that duplex grades can deliver superior life-cycle economics to marine infrastructure of vital importance, although at a higher initial price.

Another aspect of the increasing importance of corrosion management is the management of biofouling and microbial activity. Antifouling coatings, cleaning regimes, and biocidal treatments can be used to reduce the MIC and provide a more homogenous oxygen distribution at the metal-seawater interface.

Combinations of Interpretation and Engineering Implication

The reviewed studies show that the process of marine corrosion is controlled by the interplay of electrochemical, mechanical, and biological factors, instead of being controlled by one specific mechanism. Carbon steels have a low initial cost; however, they require strong and constantly monitored protection systems. Traditional stainless steels offer better resistance to localized corrosion; however, they are susceptible to localized corrosion, particularly in environments with high chloride levels, high temperatures, or the presence of microorganisms. The more expensive initial material cost can be compensated for by a longer service life, making duplex stainless steels and copper alloys properly coated with attractive options.

In terms of engineering, the findings favor the use of multi-layered corrosion management methods that integrate:

(i) Knowledgeable choice of material

(ii) Optimized design to reduce crevices and points of high stress.

(iii) Appropriate coatings and/or cathodic protection.

(iv) Continuous non-destructive and electrochemical monitoring.

This approach is critical in ensuring that the service life is prolonged, the cost of maintenance is minimized, and the reliability of structures working under unfavorable marine conditions is enhanced.

Figure 2: Classification of the reviewed studies (2020-2025) based on the primary material investigated: carbon steels, stainless steels (304L, 316L, high-grade), duplex stainless steels (S32205), aluminium alloys, and copper-based alloys.

The figure shows a comparative analysis of the rate of corrosion of different metallic materials in a very aggressive environment of 50% HCl and 4% HF in 66 o C in mg/cm 2/h with the help of a logarithmic scale. The extensive distribution of values over a number of orders of magnitude is a good indication of the vital influence of material choice on corrosion performance at extremely acidic environments.

Lunac series of high-performance alloys have the lowest corrosion rates which means it is very resistant in mixed hydrochloric-hydrofluoric acid. It is worth noting that both hardened and non-hardened Lunac alloys are better than Hastelloy B3 that is reputed to have excellent resistance to strong acids. This demonstrates the efficiency of optimized alloy structure and surface treatment in inhibiting the dissolution of metals in harsh media.

On the contrary, duplex stainless steel (1.4462), and austenitic stainless steel (1.4301) exhibit moderate corrosion resistance. Even though duplex steel is superior to traditional austenitic stainless steel, both are subject to some degree of corrosion implying that both materials are not suitable in the case of exposure to concentrated HCl/HF mixtures in the absence of extra protection.

Carbon steel (St 37-2) and hard chromium have the lowest performance, as they have extremely high rates of corrosion. This fact shows that the traditional carbon steels and the chromium-based coatings are very sensitive to application in the environment with hydrofluoric acid, and the application of it in the environment would most probably lead to the rapid material degradation and early failure.

On the whole, the figure underlines that alloy chemistry and surface condition are important determinants of the corrosion resistance in extreme acidic conditions. It makes the need for high-alloy materials or specially engineered materials quite obvious when creating components used in the highly corrosive acid mixtures.

Figure 3: Network mapping of the relationships between material category, seawater exposure conditions, experimental techniques (EIS, polarization, SEM, fatigue testing), and dominant corrosion mechanisms (pitting, MIC, SCC, corrosion fatigue).

This number demonstrates how surface machining conditions influence the susceptibility of the 316L stainless steel tube fitting nut under tensile stress in simulated seawater to surface corrosion cracking (SCC). The comparison shows that the surface roughness produced by various methods of machining has direct impact on the stress distribution, crack initiation and crack density.

The machined surface of the form tool with a low surface roughness (low Ra) will have a more homogeneous near-surface microstructure and a relatively homogeneous distribution of hardness. Consequently, tensile stress distribution is even and thus crack density is low, together with minimal hydrogen-induced cracking (HIC). The smoother surface limits stress concentration locations and limits local breakdown of the passive film, thus alleviating the initiation of SCC.

Conversely, the single-point tool machined surface with a large surface roughness (high Ra) exhibits a substantial surface irregularity and surface microstructure distortion in the vicinity of the surface. These characteristics serve as favorable locations of stress and local electrochemical action. This condition under tensile loading in simulated seawater enhances pitting corrosion, which in turn act as a source of initiation to the propagation of stress corrosion cracking further leading to a high crack density and further and wider propagation of HIC.

Generally, the figure shows that surface finish is one of the key elements in SCC resistance of austenitic stainless steels in marine conditions. The reduced machining processes also contribute greatly to the resistance against the localised corrosion and SCC as they reduce the stress concentrators and maintain the integrity of the passive film. Conversely, coarse surfaces enhance the vulnerability to mixed pitting and stress corrosion cracking in marine service significantly.

Figure 4: Quantitative visualization of the distribution of the 19 reviewed studies across material categories. Stainless steels represent the largest share of research focus, followed by carbon steels, copper alloys, duplex alloys, and aluminium.

The figure compares the maximum depth of corrosion attack (mm) of the various stainless steel and duplex alloy types in a marine environment under three temperatures (8 ^oC, 15 ^oC, and 25 ^oC). The findings clearly show that alloy composition together with temperature has a cumulative effect on the intensity of local corrosion.

Of the materials studied, 316L stainless steel has the most tremendous potential for localized attack, most specifically at 15 ^oC, where the maximum penetration depth attains its maximum value. This behavior suggests that the material is intensely temperature sensitive, and the low resistance of traditional austenitic stainless steel towards chloride localized corrosion in the marine environment.

The duplex stainless steel 2205 exhibits significantly less maximum attack depth than 316L at all temperatures, as it has better resistance, as it has a balanced austenite-ferrite type of microstructure and contains higher amounts of chromium and molybdenum. There is, however, a certain degree of temperature dependence.

Contrarily, 904L stainless steel and Ferralium (super-duplex) alloys show much better performance and have smaller depths of penetration and less sensitivity to temperature changes. 6% Mo austenitic stainless steel and Z100 exhibit the best corrosion resistance with negligible values of attack depths at all temperatures of experiment, and hence high stability of the passive film in the marine environment.

In sum, this figure highlights that the addition of alloying elements including molybdenum and nitrogen increases the resistance to localized corrosion significantly and temperature is an accelerating factor of susceptible alloys. These findings are very strong to justify the use of high-alloyed austenitic or duplex stainless steel in marine applications of critical applications, where corrosion and penetration depth are the main focus in design.

Conclusion and Recommendations

This study provides a comprehensive synthesis of recent research (2020-2025) on the corrosion behavior, mechanisms, and protection strategies for metallic materials in marine environments. The collective findings confirm that corrosion in seawater is governed by complex interactions among electrochemical, mechanical, and biological factors, making accurate prediction and control particularly challenging. Among the materials reviewed, carbon steels demonstrated the highest degradation rates. In contrast, despite enhanced alloying, austenitic stainless steels remain susceptible to localized corrosion, stress-corrosion cracking, and accelerated damage at elevated temperatures or under microbial activity. Duplex stainless steels consistently outperform conventional alloys owing to their superior passive film stability and reduced susceptibility to chloride-induced attacks.

The results also highlight the critical importance of advanced evaluation methods. Electrochemical techniques, such as EIS and potentiodynamic polarization, combined with microscopic and structural characterization (SEM and XRD), have proven essential for identifying damage initiation mechanisms and assessing the performance of coatings and alloys. These methods provided deeper insights that weight loss measurements alone could not reveal, especially in cases involving pitting, crevice corrosion, MIC, and corrosion fatigue.

These protection strategies demonstrated varying degrees of effectiveness. Surface engineering methods, including titanium infiltration and Ni-based coatings, significantly improve the resistance of stainless steel and copper alloys, respectively. Cathodic protection systems are essential for steel structures in submerged or splash-zone environments. At the same time, material selection has emerged as a decisive factor: duplex stainless steels and coated copper alloys offer superior long-term durability relative to carbon steel and aluminum in welded conditions. However, the presence of biofouling and microbiological activity has been shown to complicate corrosion behavior, underscoring the need for integrated solutions that combine coatings, mechanical design optimization, cathodic protection, and microbial control.

Overall, the synthesis of findings underscores the necessity for a multi-layered corrosion management approach that aligns material selection, protective technologies, and continuous monitoring. This integrated strategy is essential for achieving a long service life, minimizing maintenance costs, and ensuring the structural integrity of the components and systems operating in harsh marine environments. Future research should focus on real-time corrosion-monitoring technologies, hybrid protection methods, and long-term performance of emerging alloys under variable seawater conditions, thus bridging the gaps between laboratory findings and real-world engineering needs.

The collective findings of this review highlight that localized corrosion, MIC, SCC, and corrosion fatigue remain the most critical degradation mechanisms governing the material performance in marine environments. These insights directly inform the selection and implementation of corrosion-mitigation strategies. For instance, the demonstrated susceptibility of conventional austenitic stainless steels to pitting and SCC under chloride-rich or high-temperature conditions reinforces the need for more robust alloy choices, particularly duplex grades, in structural components exposed to severe marine loading. Similarly, the persistent role of MIC across multiple studies indicates that corrosion management programs should integrate biofouling control measures rather than rely solely on electrochemical protection. Moreover, the clear benefits of surface modification techniques for both stainless steels and copper alloys suggest that coating systems should be prioritized for components where localized attack or wear-corrosion coupling is expected. These evidence-based trends underlie the practical recommendations outlined in the following section.

Journal of Physics and Chemistry Research