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Article

Hydrothermal Carbonization Coating on AISI 1018 Steel for Seawater Corrosion Protection

by
Yong X. Gan
Department of Mechanical Engineering, California State Polytechnic University Pomona, 3801 W Temple Avenue, Pomona, CA 91768, USA
Coatings 2025, 15(11), 1346; https://doi.org/10.3390/coatings15111346
Submission received: 28 October 2025 / Revised: 9 November 2025 / Accepted: 18 November 2025 / Published: 19 November 2025
(This article belongs to the Special Issue Advances in Corrosion-Resistant Coatings, 2nd Edition)
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Abstract

The seawater corrosion behavior of a plain carbon steel covered with hydrothermally carbonized coating was studied. Hydrothermal carbonization of sugar (sucrose) dissolved in water with a concentration of 10 wt.% at 200 °C for 4 h was carried out to produce a carbonized coating on the steel. The corrosion resistance of the steel with and without the carbonized coating was evaluated by polarization tests in seawater. The Tafel slopes were calculated using polarization data. The corrosion current and the potential of corrosion were determined to examine the effect of the carbonized coating on the corrosion behavior of the steel. In addition, AC impedance measurements on the steel without and with the hydrothermal carbonization coating were performed in a three-electrode cell with a Ag/AgCl reference electrode, platinum counter electrode, and seawater electrolyte. It was found that hydrothermal carbonization of sugar generated a continuous carbon-rich layer on the surface of the steel. This carbon layer is highly corrosion-resistant as shown by the decrease in the corrosion current. It is concluded that the hydrothermally carbonized coating has the nature of passivation films, and it can slow down the corrosion rate of the plain carbon steel in seawater. The impedance of the steel without hydrothermal carbonization coating is very low. With hydrothermal carbonization coating, an increase in the resistance and the capacitive response of the coating/seawater interface was observed.

1. Introduction

AISI 1018 is classified as a low-carbon, mild steel. The abbreviation of AISI refers to American Iron and Steel Institute. This is one of the oldest trade associations in the United States of America’s steel producers. Its predecessor organizations date back to as early as 1855. With a balance of ductility, strength, machinability, formability, and weldability, AISI 1018 is widely used for building engineering structures. It can be carburized to achieve a hard surface and a tough core, making it suitable for manufacturing machine parts including shafts and pins. Steels are typically sensitive to chlorine ion attack through carbonation [1,2]. Similarly, AISI 1018 steel corrodes easily in brine media. It is necessary to protect the steel from corrosion in the marine environment. Recently, DNA primer inhibitors [3], carboxymethyl chitosan/L-lysine composites [4], and plant leaf extracts [5] have been applied for seawater corrosion control of steels. Trace-Mg treatments on steel [6] and Cr-Mo reinforcing steel [7] were performed to investigate their effect on the seawater corrosion behavior. The formation and evolution of Mg-Fe-CO3 layered double hydroxide in artificial seawater on construction steel were studied by Tavangar et al. [8]. The corrosion resistance of this product was also evaluated. It was found that the layered double hydroxide (LDH) can form on steel surfaces due to seawater-induced corrosion in the marine environment. The morphology of the LDH evolved from lath-like to perpendicular flakes, revealing the anisotropic growth feature. The long-term corrosion resistance of Mg-Fe-CO3 LDH in seawater was confirmed, and it showed promise for steel protection [8]. The role of marine bacteria on the corrosion of steels was reported as well [9].
Applying hydrothermally processed coatings on the surface of nonferrous alloys including copper and its alloy has been found to improve their corrosion resistance [10]. It is expected that the same approach may be applicable to ferrous alloys as well. But until now, no corrosion test result of hydrothermal carbon coating on ferrous alloys has been reported. Hydrothermal processing is an approach to synthesizing both inorganic and organic compounds and nanomaterials with hot, pressurized water as a solvent. This process is realized using sealed, high-pressure containers made of stainless steel or nickel superalloys, which allows water to be a powerful solvent for substances that are typically solid at room temperature and ambient pressure. It is widely used to produce materials like metallic oxides, silica-containing zeolites, single crystals, and various ceramics with different compositions, controlled shapes, and sizes.
Hydrothermal coatings have been investigated for increasing corrosion resistance under different environmental conditions [1,11,12]. For example, the fluoridated alkaline earth composite coatings on magnesium were hydrothermally processed for such purposes [13]. The composite coatings consist of fluoridated hydroxyapatite, magnesium hydroxide, and dittmarite. Dittmarite is a monohydrated magnesium ammonium phosphate crystal with the formula of (NH4)Mg(PO4)•H2O. The coatings were found to be very dense and uniform. Hydrothermal synthesis can be used for preparation of various coatings with diversified compositions [14]. Coatings containing simple compounds like MgCO3 and Mg(OH)2 were synthesized by soaking magnesium and/or its alloys in water solution containing NaHCO3 at a temperature of 200 °C [15]. Uniform and compact magnesium hydroxide coatings on Mg-2Zn-Mn-Ca-Ce were obtained through hydrothermal treatment of the magnesium alloy in de-ionized (DI) water at 160 °C for a certain period [16,17]. It was demonstrated by Kim et al. [18] that a lower temperature of 90 °C allowed the formation of uniform magnesium oxide coating when Mg was hydrothermally treated in a solution consisting of sodium hydroxide and Ca-EDTA (C10H12CaN2Na2O8). Many other solutions were also made for hydrothermal treatment. As an example, an ammonia nitrate aqueous solution was used for the hydrothermal processing of the AZ91D alloy, and a Mg-Al hydrotalcite coating was generated in situ at the surface of the alloy [19].
Hydrothermal treatment can be used in combination with other processing techniques either simultaneously or sequentially. For example, an AZ61 (magnesium–aluminum–zinc-based) alloy was hydrothermally treated first at 125 °C in water for 24 h followed by the growth of a butylphosphonic acid-derived self-assembled monolayer [20]. This resulted in significant improvement on the surface by 1-butylphosphonic acid with a formula of CH3CH2CH2CH2PO(OH)2.
An inorganic fluoride coating, consisting of MgF2 and MgO, was processed to increase the open circuit potential and suppress the corrosion current density of a hydrothermal hydroxyapatite (HA) coating on the AZ31 (magnesium–aluminum-based) alloy [21]. Glucose was reported to promote hydrothermal coating growth. In [22], a Ca-P coating on Mg was generated in a solution made by mixing Ca(NO3)2•4H2O (250 mM) and glucose (500 mM) first. Then, 2 mM NaOH was added to adjust the pH value to 10.0. After that, 250 mM KH2PO4 was added. The glucose-induced Ca-P coating was formed in this solution via hydrothermal treatment at 120 °C. The accumulation of corrosion products on the surface decelerated the corrosion reaction, which was also reported by Zhu et al. [23].
As mentioned above, those earlier studies indicated that the hydrothermal oxide or phosphorous coatings on nonferrous metals and their alloys can provide corrosion protection. In addition to the oxides and phosphorites, hydrothermal carbon coatings were synthesized later. They were deposited from carbohydrate solutions containing glucose, sucrose, or starch, and they have attracted significant attention. It has been shown that hydrothermal carbon coatings can be deposited uniformly on various substrates like graphite [24], silica [25], and α-Fe2O3 [26]. Moreover, it is possible to deposit hydrothermal carbon on various metallic substrates. For example, substrates containing Fe/Au [27] and Ni [28] were coated with hydrothermal carbon layers derived from sucrose and glucose. Hydrothermal carbons were found to have various applications for catalysis [28], energy conversions [29], and energy storage [30].
In this work, the applicability of hydrothermal carbon coatings for corrosion control of ferrous materials was explored. The tasks introduced here mainly focus on dealing with the effect of hydrothermally carbonized coating on the seawater corrosion resistance of the AISI-1018 low-carbon steel. Carbonization of sugar (sucrose) was realized at 200 °C for one to four hours. The generated coating was examined by optical microscopy (OM) and scanning electron microscopy (SEM). The seawater corrosion behavior of the steel with and without the hydrothermal carbonization coating was evaluated using electrochemical measurement results. The Tafel slopes, corrosion current, and potential were determined.

2. Materials and Methods

AISI 1018 steel with a nominal carbon content of less than 0.20 wt.% was purchased from McMaster Carr Inc. in Santa Fe Spring, CA, USA. It is supplied in the cold-rolled state, resulting in better surface finish and improved mechanical properties than other supplied states. Its hardness on the HRB scale is 117. There are many AISI 1018 steel equivalents. The US equivalents include ASTM A29, ASTM A512, and ASTM A108, as well as MIL S-11310 (CS 1018) and AMS 5069. Some international equivalents can also be given. They are EN 1.7218 (Germany), BS 970 708A30 (UK), and JIS SCM 420 (Japan), among others. The chemical composition of AISI 1018 is close to that of ASTM A36 steel. Table 1 lists the major element contents provided by the supplier. Besides the major alloying element, the rest is iron.
Sugar (sucrose) powder was purchased from a Wal-Mart shopping center located at Diamond Bar, CA, USA. A CHI6005E electrochemical workstation bought from CH Instrument, Austin, TX, USA, was used for polarization measurements and alternating current (AC) impedance data acquisition. The hydrothermal carbonization was conducted using a 25 mL stainless steel hydrothermal reactor made by Col-Int Tech, Irmo, SC, USA. The specimens with a dimension of 50 mm × 10 mm × 2 mm were immersed into a 10% sugar water solution and encapsulated into the stainless steel reactor. The reactor was heated up to 200 °C and held for 4 h. The pressure was monitored at 1 MPa approximately. After hydrothermal carbonization, the treated specimens held in the reactor were cooled down to a room temperature of 25 °C in cold water flow. After that, the specimens were taken out from the reactor, washed in clean water, and dried in flowing air. The specimen preparation and hydrothermal carbonization procedures can be found in Scheme 1.
The seawater used for the corrosion test was the natural seawater fetched from the Pacific Ocean near Monterey Bay, CA, USA. The nominal salinity was about 3.5 wt.% NaCl. The pH value was about 8.1. The temperature for the corrosion test was an ambient temperature of 25 °C.
Both coated and uncoated specimens were imaged using a Canon T6 camera (Tokyo, Japan), RH-2000 optical microscope, and a JEOL JSM-6010PLUS/LA (Tokyo, Japan) scanning electron microscope (SEM). The elemental analysis of the coating was performed using the same SEM. Seawater corrosion tests on the coated and uncoated steel specimens were conducted at room temperature in seawater using Ag/AgCl in 1.0 M KCl as the reference electrode and a 1.0 mm diameter Pt wire as the counter electrode connected to the CHI6005E made by CH Instruments, Inc., Austin, TX, USA. In addition, the AC impedance measurements were performed in seawater using the same CHI6005E Electrochemical Workstation. The frequency range for the measurements was from 1 to 100,000 Hz. The AC amplitude was 5 mV.

3. Results and Discussion

3.1. Microstructure and Composition of the Hydrothermal Carbonization Coating

The optical image of the low-carbon steel specimen is presented in Figure 1a. The surface shows a metal luster. Figure 1b is the image of the carbonized coating. The thickness of the coating is about 50 microns. The surface was found to be completely covered by carbon black. To reveal microstructures more clearly, the optical micrographs of both uncoated and coated AISI 1018 steel specimens after corrosion in seawater were captured by the RH-2000 microscope and shown in Figure 2. Figure 2a presents a low magnification micrograph of the uncoated specimen after the seawater corrosion test. Due to the active ionization of Fe in the anodic polarization cycle, the surface of the specimen is clean except for those tiny pits generated by the pitting corrosion under the action of chlorine ion. Such a characteristic can also be seen from Figure 2b for the uncoated steel at a higher magnification. Figure 2c reveals the microstructure of the hydrothermal carbon-coated steel at a low magnification. After the anodic polarization, the hydrothermal coating still partially covers the surface of the steel. At a higher magnification, as shown in Figure 2d, the coated area (upper left part of the image) contains ridgelines, representing the carbon in the hydrochar form. The steel exposed region at the lower right corner of the image shows the pitting corrosion feature generated by chlorine ion corrosion.
Figure 3a is the SEM image of the carbonized coating. The length of the red color scale bar is 50 mm. The features of initiation and growth of carbon were revealed by the ridges and aggregates on the surface of the steel. The initial growth of the hydrothermally formed carbon was characterized by the formation of clusters of hydrochar seeds. The growth of the seeds built up a connection between them and formed a continuous coating. To confirm the formation of carbon in the coating, elemental analysis of the surface was performed using the energy-dispersive X-ray diffraction spectroscopy. Area mapping spectrum results can be found in Figure 3b. The major composition includes iron and carbon. Oxygen was also found, as shown by the energy peak around 0.5 keV. The sources of oxygen signal include the surface oxidization of the steel and the hydroxyl group of both hydrochar and iron hydroxides. Since the hydrochar coating was covered with a very thin layer of gold to prevent charge build-up on the surface, the signal of gold was detected as shown by the Au peaks in the energy-dispersive spectrum of Figure 3b. A trivial amount of aluminum was detected as an impurity in the coating.

3.2. Seawater Corrosion Behavior of the Hydrothermal Carbonization Coating

The polarization testing results are presented in Figure 4. Figure 4a shows both anodic and cathodic polarization of the as-received plain carbon steel without hydrothermal carbonization treatment. In this figure, both the anodic and cathodic polarization branches indicate that the seawater corrosion of the steel is under electrochemical reaction control. This provides the basis for the following electrochemical analysis using the quantitative corrosion theory [31]. After the hydrothermal coating was generated on the steel surface as shown in Figure 1b and Figure 3a, polarization tests were conducted again to generate the results, as shown in Figure 4b. Although the general trend is still under electrochemical reaction control, some vertically aligned data clusters in Figure 4b suggest the passivation effect of the carbonized coating.

3.3. Tafel Constants

The quantitative corrosion theory [31] was used for extracting parameters including open circuit potential, Tafel constants, and corrosion current for evaluating the corrosion behavior of the steel specimens with and without the hydrothermally carbonized coating. Since the rates of anodic and cathodic electrochemical reactions are controlled by charge transfer, the measured current (i) in the electrochemical cell can be expressed as
i = i c o r r e x p 2.303 E − E c o r r β a − e x p 2.303 E − E c o r r β c
where
  • icorr is the corrosion current in amperes per unit area (A/cm2 in this work);
  • Ecorr is the corrosion potential in volts vs. the Ag/AgCl reference electrode;
  • E is the electrode potential in volts vs. the Ag/AgCl reference electrode;
  • βa and βc are the anodic and cathodic β Tafel constants in volts per decade.
During seawater corrosion of the 1018 steel, iron ionization is the major reaction at the anode. When the potential is close to the corrosion potential, the relationship as described by Equation (1) can be approximated by straight lines. In Figure 4, the polarization data were extrapolated to generate the straight lines to extract the useful parameters such as the corrosion current (icorr), the corrosion potential (Ecorr), the anodic β Tafel constant (βa), and the cathodic β Tafel constant (βc). Their values are listed in Table 2. We can see from the results in Table 2 that there is no obvious shift in the corrosion potential due to the carbonized coating. However, the corrosion current of the specimen with carbon coating is about one million times less than that of the steel without hydrothermal carbon coating. Therefore, it is concluded that the hydrothermally carbonized coating just like a conversion film caused the increase in the polarization resistance and slowed down the seawater corrosion of the steel.

3.4. Electrochemical Impedance

Figure 5 reveals the AC impedance of the AISI 1018 steel in seawater. The seawater/steel double layer demonstrates the resistive behavior with Z′ (the real part of impedance) value of about 1 Ohm, as shown in Figure 5a. The imaginary part of the impedance, Z″, is close to zero, as can be seen from Figure 5b. This further proves that the steel/electrolyte interface is indeed purely resistive at the lower-frequency range of 1 Hz to 5000 Hz. In the higher-frequency range from 5000 to 100,000 Hz, there is a small increase in the imaginary impedance value (less than 0.1 Ohm). This behavior is inductive in nature, which is associated with the frequency response of the iron ion, hydroxide group, and chlorine ion in seawater. The Bode plot of the steel/seawater system in Figure 5c shows the phase angle shift of 6 degrees approximately in the high-frequency range from 5000 to 100,000 Hz. Figure 5d, the Nyquist plot, shows the consistent resistive response nature of the electrode/electrolyte interface because all the data points are crowded together at the real axis. The estimated real part of the impedance is about 0.85 Ohm.
To examine the hydrothermal carbonization coating effect, the steel with hydrothermal carbonization treatment was also characterized by the AC impedance technique. The results are shown in Figure 6. The seawater/steel double layer demonstrates both resistive and capacitive responses. The Z′ values of the coated steel/seawater interface at different frequencies fall into the range from 1.5 to 2.5 Ohm, as shown in Figure 6a. The absolute value of the imaginary part of the impedance, Z″, changes slightly from zero to 0.4 Ohm as the frequency increases, as can be found in Figure 6b. The coated steel/electrolyte interface is resistive at the lower-frequency range of 1 Hz to 100 Hz. In the higher-frequency range from 100 to 100,000 Hz, there is an obvious drop in the imaginary impedance value (to less than −0.4 Ohm). This behavior is capacitive, indicating the hydrothermal carbon coating as a continuous film. The Bode plot of the coated steel/seawater system in Figure 6c reveals the phase angle shift from 0 to −14 degrees approximately in the high-frequency range from 100 to 100,000 Hz. Figure 6d, the Nyquist plot, further demonstrates the resistive and capacitive responses. The estimated real part of the impedance is about 2.4 Ohm. It is noted that there are two half circles instead of two full circles in the Nyquist plot, as shown in Figure 6d. It is possibly due to the unstable ion charge–discharge at the internal walls of the hydrochar pores.
Based on the results on the Nyquist plots of Figure 5d and Figure 6d, the equivalent circuits for the coated and uncoated steel/seawater cells can be established, respectively. The uncoated steel/seawater double layer can be modeled by the circuit, as shown in Figure 7a. Here, we used the notation introduced in [32] to represent the resistance element and capacitor element. Ru is the resistance from the seawater electrolyte, which is equal to 0.85 Ohm. Polarization resistance, Rp ≈ 0.05 Ohm, can be determined by the imaginary part of the impedance, as shown in Figure 5d. Such a low value of Rp indicates that the uncoated steel tends to corrode easily in seawater. The hydrothermal carbon-coated steel/seawater double layer shows complexity in response to AC signals. The proposed equivalent circuit is shown in Figure 7b. The Ru value is about 1.25 Ohm, as can be determined from the Nyquist plot shown in Figure 6d. The Rp value is about 0.75 Ohm. Obviously, this value is about 25 times higher than that for the uncoated steel in seawater. Therefore, the hydrothermal carbon-coated specimen has much higher resistance to seawater corrosion than the uncoated specimen. The R2 value is found from the second circle in Figure 6d to be 0.5 Ohm approximately. The physical meaning of C2 is still not clear. It may be due to the pore formation in the hydrothermal carbon layer. The absorption and desorption of ions within the pores in the carbon layer contributed to the capacitive response, as measured and shown by the second half circles in the Nyquist plot of Figure 6d.
Hydrothermal carbonization-generated coating in the form of hydrochar demonstrated corrosion protection through the test on the AISI 1018 steel in seawater. The hydrothermal processing method is environmentally friendly because the water solvent is encapsulated in reactors. There is no risk of harmful fluid leaking from the process. The residue liquid may be used as fertilizer in agriculture [33].

4. Conclusions

Hydrothermal carbonization of 10 wt.% sugar generated a continuous carbon-rich layer on the surface of the AISI 1018 low-carbon steel. This carbon layer is just like a conversion film, causing a significant decrease in the corrosion current. The hydrothermal carbonization treatment can slow down the seawater corrosion of the steel. The corrosion resistance of the steel with coating is about one million times higher than that of the steel without the carbonized coating, as indicated by the comparison of their corrosion current values. The AC impedance measurement on the steel without coating indicates resistive behavior. The steel with hydrothermal carbonization coating is both resistive and capacitive. The impedance of the steel without hydrothermal carbonization coating has a very low value of 0.85 Ohm. With hydrothermal carbonization coating, an increase in the resistance to 1.25 Ohm is shown. It is found that there are two half circles instead of two full circles in the Nyquist plot for the coated specimen in seawater indicating the unstable charge–discharge behavior of ions in the hydrochar pores.

Funding

This research was funded by US National Science Foundation under Grant Number CMMI-2436148.

Data Availability Statement

Data supporting reported results can be made available upon request.

Acknowledgments

The author thanks Corey R. Grice from the Center for Materials & Sensor Characterization, College of Engineering, The University of Toledo, 1700 N Westwood Ave, University of Toledo, Toledo, OH 43606-3390, USA, for his assistance in taking the SEM image and performing the composition analysis.

Conflicts of Interest

The author declares no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

References

  1. Crespi, P.; Zucca, M.; Valente, M.; Longarini, N. Influence of corrosion effects on the seismic capacity of existing RC bridges. Eng. Fail. Anal. 2022, 140, 106546. [Google Scholar] [CrossRef]
  2. Zhao, Y.F.; Hu, X.; Zhao, X.L.; Zhang, G.Z.; Shi, C.J. Chloride induced corrosion behavior of carbon steel rebar in seawater mixed Portland cement-SF-MK ternary pastes with low w/b ratio. Cem. Concr. Compos. 2025, 163, 106182. [Google Scholar] [CrossRef]
  3. Yang, G.H.; Liu, H.Q.; Zhong, H.X.; Bai, Z.P.; Zhi, F.F.; Chen, Q.; Zhu, P.F.; Liu, X.; Chu, H.Q.; Jiang, L.H. Inhibition properties and mechanism of DNA primer inhibitor for Q355 mild steel corrosion in simulated seawater. Surf. Interface 2025, 75, 107759. [Google Scholar] [CrossRef]
  4. Wang, H.Y.; Liang, Z.P.; Wang, Y.Y.; Jin, H.; Cao, H.Y.; Yang, C.C. Sustainable corrosion inhibition of EH40 steel in seawater using carboxymethyl chitosan/L-lysine composite. J. Environ. Chem. Eng. 2025, 13, 119271. [Google Scholar] [CrossRef]
  5. Dobo, K.I.; Sarkodie, K.; Agyei, E.; Adenutsi, C.D. Assessing the corrosion inhibition potential of novel green and sustainable plant leaf extracts on mild steel in seawater—Preliminary studies. Next Res. 2025, 2, 100548. [Google Scholar] [CrossRef]
  6. Yang, G.M.; Huang, T.J.; Sun, B.Z.; Wang, Y.S.; Liu, C.; Huang, F.; Liu, Z.Y.; Du, C.W.; Li, X.G. Effect of trace-Mg treatment on stress corrosion cracking behavior of different heat-affected zone microstructures of X70 steel in simulated seawater. Corros. Sci. 2026, 258, 113437. [Google Scholar] [CrossRef]
  7. Xin, Z.G.; Guo, L.; Wang, F.J.; Luo, Q.; Wang, L.G.; Chen, H.D.; Liu, Z.Y.; Jiang, J.Y. Insights into the corrosion resistance of Cr-Mo alloy reinforcing steel in simulated pore solution and real seawater sea-sand concrete: A preliminary study. Case Stud. Constr. Mater. 2025, 23, e05002. [Google Scholar] [CrossRef]
  8. Tavangar, R.; Geyter, N.D.; Verbeken, K.; Depover, T. Elucidating the natural evolution of Mg-Fe-CO3 layered double hydroxide in artificial seawater on construction steel and its corrosion resistance. Eng. Fail. Anal. 2025, 182, 110061. [Google Scholar] [CrossRef]
  9. Jaume, J.; Mercier, D.; Seyeux, A.; Semetey, V.; Zanna, S.; Marcus, P. Dual role of marine bacteria Pseudoalteromonas NCIMB 2021 in corrosion of mild steel in artificial seawater. Corros. Sci. 2025, 255, 113076. [Google Scholar] [CrossRef]
  10. Gan, Y.X.; Chang, Y.; Chen, C.-C.; Li, M.; Gan, J.B.; Li, J. Seawater corrosion of copper and its alloy coated with hydrothermal carbon. Coatings 2022, 12, 798. [Google Scholar] [CrossRef]
  11. Li, L.Y.; Cui, L.Y.; Liu, B.; Zeng, L.C.; Chen, X.B.; Li, S.Q.; Wang, Z.L.; Han, E.H. Corrosion resistance of glucose-induced hydrothermal calcium phosphate coating on pure magnesium. Appl. Surf. Sci. 2019, 465, 1066–1077. [Google Scholar] [CrossRef]
  12. Lin, Y.; Cai, S.; Jiang, S.; Xie, D.; Ling, R.; Sun, J.; Wei, J.; Shen, K.; Xu, G. Enhanced corrosion resistance and bonding strength of Mg substituted β-tricalcium phosphate/Mg(OH)2 composite coating on magnesium alloys via one-step hydrothermal method. J. Mech. Behav. Biomed. Mater. 2019, 90, 547–555. [Google Scholar] [CrossRef]
  13. Jiang, Y.Y.; Zhu, L.G.; Cai, S.; Shen, S.B. Corrosion-resistant fluoridated Ca-Mg-P composite coating on magnesium alloys prepared via hydrothermal assisted sol-gel process. J. Mater. Res. 2018, 33, 3793–3800. [Google Scholar] [CrossRef]
  14. Gan, Y.X.; Jayatissa, A.H.; Yu, Z.; Chen, X.; Li, M.H. Hydrothermal synthesis of nanomaterials. J. Nanomater. 2020, 2020, 8917013. [Google Scholar] [CrossRef]
  15. Xie, J.S.; Zhang, J.H.; Liu, S.J.; Li, Z.H.; Zhang, L.; Wu, R.Z.; Hou, L.G.; Zhang, M.L. Hydrothermal synthesis of protective coating on Mg alloy for degradable implant applications. Coatings 2019, 9, 160. [Google Scholar] [CrossRef]
  16. Song, D.; Guo, G.H.; Jiang, J.H.; Zhang, L.W.; Ma, A.B.; Ma, X.L.; Chen, J.Q.; Cheng, Z.J. Hydrothermal synthesis and corrosion behavior of the protective coating on Mg-2Zn-Mn-Ca-Ce alloy. Prog. Nat. Sci. Mater. Int. 2016, 26, 590–599. [Google Scholar] [CrossRef]
  17. Song, D.; Li, C.; Zhang, L.W.; Ma, X.L.; Guo, G.H.; Zhang, F.; Jiang, J.H.; Ma, A.B. Decreasing bio-degradation rate of the hydrothermal-synthesizing coated Mg alloy via pre-solid-solution treatment. Materials 2017, 10, 858. [Google Scholar] [CrossRef] [PubMed]
  18. Kim, S.Y.; Kim, Y.K.; Ryu, M.H.; Bae, T.S.; Lee, M.H. Corrosion resistance and bioactivity enhancement of MAO coated Mg alloy depending on the time of hydrothermal treatment in Ca-EDTA solution. Sci. Rep. 2017, 7, 9061. [Google Scholar] [CrossRef] [PubMed]
  19. Wang, L.D.; Zhang, K.Y.; Sun, W.; Wu, T.T.; He, H.R.; Liu, G.C. Hydrothermal synthesis of corrosion resistant hydrotalcite conversion coating on AZ91D alloy. Mater. Lett. 2013, 106, 111–114. [Google Scholar] [CrossRef]
  20. Wang, C.W.; Liu, C.; Lin, D.J.; Yeh, M.L.; Lee, T.M. Hydrothermal treatment and butylphosphonic acid derived self-assembled monolayers for improving the surface chemistry and corrosion resistance of AZ61 magnesium alloy. Sci. Rep. 2017, 7, 16910. [Google Scholar] [CrossRef]
  21. Zhang, C.Y.; Ma, Y.L.; Liu, C.L. Hydroxyapatite coating on fluorine-treated magnesium alloy by hydrothermal method and its electrochemical corrosion behaviour in Hank’s solution. Prot. Met. Phys. Chem. Surf. 2019, 55, 127–135. [Google Scholar] [CrossRef]
  22. Ling, L.; Cai, S.; Li, Q.Q.; Sun, J.Y.; Bao, X.G.; Xu, G.H. Recent advances in hydrothermal modification of calcium phosphorus coating on magnesium alloy. J. Magnes. Alloys 2022, 10, 62–81. [Google Scholar] [CrossRef]
  23. Zhu, Y.Y.; Wu, G.M.; Zhao, Q.; Zhang, Y.H.; Xing, G.J.; Li, D.L. Anticorrosive magnesium hydroxide coating on AZ31 magnesium alloy by hydrothermal method. J. Phys. Conf. Ser. 2009, 188, 12044. [Google Scholar] [CrossRef]
  24. Roldan, L.; Santos, I.; Armenise, S.; Fraile, J.M.; Garcıa-Bordeje, E. The formation of a hydrothermal carbon coating on graphite microfiber felts for using as structured acid catalyst. Carbon 2012, 50, 1363–1372. [Google Scholar] [CrossRef]
  25. Titirici, M.M.; Thomas, A.; Antonietti, M. Replication and coating of silica templates by hydrothermal carbonization. Adv. Funct. Mater. 2007, 17, 1010–1018. [Google Scholar] [CrossRef]
  26. Wang, Z.Y.; Luan, D.Y.; Madhavi, S.; Hu, Y.; Lou, X.W. Assembling carbon-coated α-Fe2O3 hollow nanohorns on the CNT backbone for superior lithium storage capability. Energy Environ. Sci. 2012, 5, 5252–5256. [Google Scholar] [CrossRef]
  27. Wang, Z.F.; Xiao, P.F.; He, N.Y. Synthesis and characteristics of carbon encapsulated magnetic nanoparticles produced by a hydrothermal reaction. Carbon 2006, 44, 3277–3284. [Google Scholar] [CrossRef]
  28. Ashik, U.P.M.; Asano, S.; Kudo, S.; Minh, D.P.; Appari, S.; Hisahiro, E.; Hayashi, J. The distinctive effects of glucose-derived carbon on the performance of Ni-based catalysts in methane dry reforming. Catalysts 2020, 10, 21. [Google Scholar] [CrossRef]
  29. Teng, F.; Hu, Z.H.; Ma, X.H.; Zhang, L.C.; Ding, C.X.; Yu, Y.; Chen, C.H. Hydrothermal synthesis of plate-like carbon-coated Li3V2(PO4)3 and its low temperature performance for high power lithium ion batteries. Electrochim. Acta 2013, 91, 43–49. [Google Scholar] [CrossRef]
  30. Pei, B.; Wang, Q.; Zhang, W.X.; Yang, Z.H.; Chen, M. Enhanced performance of LiFePO4 through hydrothermal synthesis coupled with carbon coating and cupric ion doping. Electrochim. Acta 2011, 56, 5667–5672. [Google Scholar] [CrossRef]
  31. Marcus, P. Corrosion Mechanisms in Theory and Practices, 3rd ed.; CRC Press: Boca Raton, FL, USA, 2012; p. 47. [Google Scholar]
  32. Lazanas, A.C.; Prodromidis, M.I. Electrochemical impedance spectroscopy—A tutorial. ACS Meas. Sci. 2023, 3, 162–193. [Google Scholar] [CrossRef] [PubMed]
  33. Yuan, T.; Cheng, Y.F.; Huang, W.W.; Zhang, Z.Y.; Lei, Z.F.; Shimizu, K.; Utsumi, M. Fertilizer potential of liquid product from hydrothermal treatment of swine manure. Waste Manag. 2018, 77, 166–171. [Google Scholar] [CrossRef] [PubMed]
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Figure 1. Photographs of uncoated steel (a) and coated steel (b).
Figure 1. Photographs of uncoated steel (a) and coated steel (b).
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Figure 2. Micrographs of specimens after seawater corrosion. (a) Uncoated steel at low magnification, (b) uncoated steel at higher magnification, (c) coated steel at low magnification, and (d) coated steel at higher magnification.
Figure 2. Micrographs of specimens after seawater corrosion. (a) Uncoated steel at low magnification, (b) uncoated steel at higher magnification, (c) coated steel at low magnification, and (d) coated steel at higher magnification.
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Figure 3. SEM image of the coated steel (a) and the EDX spectrum (b).
Figure 3. SEM image of the coated steel (a) and the EDX spectrum (b).
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Figure 4. Corrosion tests results for uncoated specimen (a) and coat specimen (b).
Figure 4. Corrosion tests results for uncoated specimen (a) and coat specimen (b).
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Figure 5. AC impedance measurement results of steel without hydrothermal carbonization coating: (a) the real part, (b) the imaginary part, (c) Bode plot, and (d) Nyquist plot.
Figure 5. AC impedance measurement results of steel without hydrothermal carbonization coating: (a) the real part, (b) the imaginary part, (c) Bode plot, and (d) Nyquist plot.
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Figure 6. AC impedance measurement results of steel with hydrothermal carbonization coating: (a) the real part, (b) the imaginary part, (c) Bode plot, and (d) Nyquist plot.
Figure 6. AC impedance measurement results of steel with hydrothermal carbonization coating: (a) the real part, (b) the imaginary part, (c) Bode plot, and (d) Nyquist plot.
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Figure 7. Equivalent circuits (Randles circuits) of (a) uncoated steel/seawater electrochemical cell and (b) hydrothermal carbon-coated steel/seawater electrochemical cell.
Figure 7. Equivalent circuits (Randles circuits) of (a) uncoated steel/seawater electrochemical cell and (b) hydrothermal carbon-coated steel/seawater electrochemical cell.
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Scheme 1. Specimen preparation and hydrothermal carbonization flow chart.
Scheme 1. Specimen preparation and hydrothermal carbonization flow chart.
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Table 1. Major alloying element contents in the AISI 1018 steel.
Table 1. Major alloying element contents in the AISI 1018 steel.
Element TypeCarbon (C)Manganese (Mn)Phosphorus (P)Sulfur (S)
Content (wt.%)0.15~0.200.60~0.90<0.05<0.04
Table 2. Tafel constant, corrosion current, and corrosion potential results.
Table 2. Tafel constant, corrosion current, and corrosion potential results.
Specimen Typeβc (V/dec)βa (V/dec)icorr (A/cm2)Ecorr (V)
With coating−0.7131.2157.943 × 10−11−0.655
Without coating−0.1620.0638.642 × 10−5−0.627
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Gan, Y.X. Hydrothermal Carbonization Coating on AISI 1018 Steel for Seawater Corrosion Protection. Coatings 2025, 15, 1346. https://doi.org/10.3390/coatings15111346

AMA Style

Gan YX. Hydrothermal Carbonization Coating on AISI 1018 Steel for Seawater Corrosion Protection. Coatings. 2025; 15(11):1346. https://doi.org/10.3390/coatings15111346

Chicago/Turabian Style

Gan, Yong X. 2025. "Hydrothermal Carbonization Coating on AISI 1018 Steel for Seawater Corrosion Protection" Coatings 15, no. 11: 1346. https://doi.org/10.3390/coatings15111346

APA Style

Gan, Y. X. (2025). Hydrothermal Carbonization Coating on AISI 1018 Steel for Seawater Corrosion Protection. Coatings, 15(11), 1346. https://doi.org/10.3390/coatings15111346

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