Comparative Study on TiCN-Coated Stainless Steels: Enhancing Corrosion Resistance for Geothermal Engineering Applications

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Geothermal energy systems expose metallic components to aggressive environments containing chloride ions, elevated temperatures, and corrosive fluids that accelerate material degradation. Selecting suitable engineering materials with superior corrosion resistance is therefore essential for improving equipment reliability and extending service life. The reviewed study investigates the corrosion behavior of TiCN-coated ferritic (SS 11-0) and austenitic (SS 18-8) stainless steels intended for geothermal drilling applications. Using Physical Vapor Deposition (PVD), combined with microstructural characterization, hardness evaluation, salt spray testing, and electrochemical polarization measurements, the research compares the protective performance of both substrates. The findings demonstrate that TiCN-coated SS 18-8 provides superior corrosion resistance, highlighting its potential as a durable material for geothermal engineering under neutral corrosive conditions.

Bibliographic Information

Item Information
Article Title Comparative study on the corrosion behavior of TiCN-coated austenitic and ferritic stainless steels in geothermal environments
Authors Agus Solehudin; Haipan Salam; Enda Permana; Atiek Rostika Noviyanti; Akrajas Ali Umar; Risti Ragadhita
Journal Teknomekanik
Volume 9
Issue 2
Publication Year 2026
Pages 137–161
DOI https://doi.org/10.24036/teknomekanik.v9i2.44172
Publisher Universitas Negeri Padang
License Creative Commons Attribution 4.0 International (CC BY 4.0)
e-ISSN 2621-8720
p-ISSN 2621-9980
Keywords corrosion resistance; geothermal condition; PVD; polarization resistance; stainless steel; weight loss

Research Background

The rapid expansion of geothermal energy has increased the demand for structural materials capable of maintaining mechanical integrity under chemically aggressive operating conditions. Geothermal wells expose drilling tools, pipelines, and supporting equipment to high temperatures and corrosive fluids containing chloride ions, sulfates, dissolved gases, and acidic species. These conditions accelerate corrosion, shorten component lifespan, and increase maintenance costs.

Stainless steel has long been recognized as one of the preferred engineering materials for geothermal applications because of its ability to form a passive chromium oxide layer that protects against corrosion. Nevertheless, its corrosion resistance varies considerably according to alloy composition. Ferritic stainless steels generally contain lower chromium and negligible nickel contents, whereas austenitic grades contain higher concentrations of chromium and nickel that promote a more stable passive layer and improved durability under aggressive environments.

Various surface engineering techniques have been developed to further improve stainless steel performance. Among these, titanium carbonitride (TiCN) coatings deposited using Physical Vapor Deposition (PVD) have attracted significant attention because they provide high hardness, excellent wear resistance, low friction, and enhanced corrosion protection. Despite numerous investigations on coating microstructure and mechanical properties, comparatively fewer studies have systematically examined how different stainless steel substrates influence the corrosion performance of TiCN coatings.

The reviewed research addresses this knowledge gap by comparing TiCN-coated ferritic SS 11-0 and austenitic SS 18-8 under simulated geothermal corrosion conditions. Beyond conventional salt spray testing, the study incorporates electrochemical polarization measurements to quantitatively evaluate corrosion kinetics, enabling a more comprehensive assessment of coating performance and substrate–coating interactions.

Research Objective

  • To evaluate the corrosion behavior of ferritic stainless steel (SS 11-0) and austenitic stainless steel (SS 18-8) before and after TiCN coating.
  • To investigate the influence of TiCN deposition time on coating thickness, hardness, and corrosion resistance.
  • To characterize the morphology and elemental composition of TiCN-coated stainless steels using FESEM–EDS analysis.
  • To quantify corrosion performance through both mass-loss measurements and electrochemical polarization resistance testing.
  • To compare the suitability of TiCN-coated ferritic and austenitic stainless steels for geothermal engineering applications operating under neutral corrosive environments.

Why This Research Matters

  • Supports geothermal energy development. Improving corrosion resistance contributes to longer-lasting drilling and production equipment, reducing operational interruptions and maintenance costs.
  • Advances corrosion engineering. The study provides comparative evidence regarding the influence of substrate composition on the effectiveness of TiCN protective coatings.
  • Strengthens material selection. Engineers gain quantitative information for selecting stainless steel substrates capable of maintaining structural integrity in aggressive geothermal environments.
  • Demonstrates the effectiveness of PVD coatings. The research confirms that TiCN coatings substantially improve surface hardness and corrosion protection while maintaining coating uniformity.
  • Integrates complementary characterization techniques. Mechanical testing, microstructural analysis, salt spray exposure, weight-loss measurements, and electrochemical polarization collectively provide a comprehensive evaluation of coating performance.
  • Contributes to sustainable infrastructure. Improved corrosion resistance can extend component service life, reduce material replacement frequency, and enhance the long-term sustainability of geothermal facilities.
  • Provides practical engineering guidance. The findings demonstrate that TiCN-coated SS 18-8 offers superior corrosion performance compared with TiCN-coated SS 11-0, making it a promising candidate for demanding geothermal applications.

Research Methodology

This study employed an experimental materials engineering approach to compare the corrosion performance of TiCN-coated ferritic and austenitic stainless steels under simulated geothermal conditions. The research integrated coating deposition, physicochemical characterization, mechanical evaluation, accelerated corrosion testing, and electrochemical analysis to examine how substrate composition influences coating performance. The experimental workflow enabled a comprehensive assessment of coating quality, corrosion resistance, and mechanical properties.

Materials

  • Two stainless steel substrates were investigated: SS 11-0 (ferritic stainless steel) and SS 18-8 (austenitic stainless steel).
  • SS 18-8 contains higher chromium and nickel contents than SS 11-0, providing a stronger passive oxide layer and potentially superior corrosion resistance.
  • The stainless steel specimens were prepared according to ASTM G1-03(2017)e1 before coating to ensure clean and uniform surfaces.

TiCN Coating Process

  • Titanium Carbonitride (TiCN) coatings were deposited using the Physical Vapor Deposition (PVD) technique.
  • Deposition was performed inside a high-vacuum chamber at approximately 250 °C and a pressure of approximately 1 × 10−5 Torr.
  • Three coating durations—15, 25, and 35 minutes—were applied to investigate the influence of deposition time on coating characteristics.

Surface and Material Characterization

  • Field Emission Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (FESEM–EDS) was used to evaluate coating morphology and elemental composition.
  • Coating thickness was measured using a Fischerscope® X-RAY XAN instrument.
  • Surface hardness was determined through Vickers microhardness testing to assess the mechanical improvement provided by the TiCN coating.

Corrosion Evaluation

  • Accelerated corrosion testing followed ASTM B117 using a neutral salt spray containing 5% NaCl for 100 hours.
  • Corrosion rates were calculated using the ASTM G31 mass-loss method.
  • Electrochemical corrosion behavior was evaluated using linear polarization resistance (LPR) with a potentiostat employing a three-electrode configuration.
  • Corrosion current density, polarization resistance, and corrosion rate were calculated to quantify coating performance.

Experimental Analysis

The researchers compared coated and uncoated specimens by examining coating thickness, hardness, elemental distribution, surface morphology, corrosion products, weight loss, and electrochemical parameters. These complementary analyses enabled a comprehensive comparison between ferritic and austenitic stainless steels after TiCN coating under simulated geothermal corrosion conditions.

Key Findings

TiCN Coatings Were Successfully Deposited on Both Stainless Steel Substrates

FESEM–EDS analysis confirmed the successful formation of TiCN coatings on both SS 11-0 and SS 18-8 substrates. After coating, titanium, nitrogen, carbon, and oxygen dominated the surface composition, while signals originating from the underlying substrate became significantly weaker, indicating effective surface coverage.

Longer Deposition Time Improved Coating Quality

Increasing the deposition duration resulted in thicker TiCN coatings and improved coating quality. Thicker coatings exhibited better surface protection and contributed to enhanced hardness and corrosion resistance, demonstrating the importance of deposition time in optimizing coating performance.

Surface Morphology Changed Significantly After Coating

Prior to coating, both stainless steel substrates displayed machining grooves and exposed surfaces susceptible to corrosion. Following TiCN deposition, the surfaces became considerably smoother and more homogeneous. Although small pinholes and macroparticles remained visible, the coatings substantially reduced direct exposure of the substrates to corrosive environments.

SS 18-8 Exhibited Superior Coating Performance

Among the investigated substrates, TiCN-coated SS 18-8 consistently demonstrated superior hardness, better coating uniformity, and higher corrosion resistance than TiCN-coated SS 11-0. The higher chromium and nickel contents in SS 18-8 promoted the formation of a more stable passive layer, complementing the protective function of the TiCN coating.

Corrosion Rates Were Significantly Reduced by TiCN Coating

Mass-loss measurements showed that TiCN coating effectively reduced corrosion rates on both stainless steels. The coated SS 18-8 specimen exhibited the lowest corrosion rate among all tested materials, indicating that the combination of TiCN coating and an austenitic substrate provides the greatest corrosion protection under neutral corrosive conditions.

Electrochemical Measurements Confirmed Improved Corrosion Resistance

Linear polarization resistance testing demonstrated lower corrosion current densities and higher polarization resistance values for coated specimens than for uncoated specimens. These electrochemical results independently confirmed the protective effectiveness of the TiCN coating and were consistent with the mass-loss observations.

Substrate Composition Strongly Influenced Coating Performance

The comparative analysis revealed that substrate composition plays an important role in determining the effectiveness of TiCN coatings. Austenitic SS 18-8 provided a more favorable substrate for coating adhesion and long-term corrosion resistance than ferritic SS 11-0 because of its higher chromium and nickel contents.

Scientific Contribution

  • Provides a systematic comparison between TiCN-coated ferritic and austenitic stainless steels under simulated geothermal corrosion conditions.
  • Demonstrates the synergistic interaction between substrate alloy composition and TiCN protective coatings in improving corrosion resistance.
  • Integrates microstructural characterization, mechanical evaluation, accelerated corrosion testing, and electrochemical measurements into a comprehensive corrosion assessment framework.
  • Shows that electrochemical polarization testing complements conventional mass-loss methods for evaluating coating performance.
  • Expands current knowledge regarding the influence of stainless steel substrate composition on TiCN coating effectiveness.
  • Provides experimental evidence supporting the use of TiCN-coated SS 18-8 as a high-performance material for corrosive geothermal environments.

Industrial Implications

  • The findings provide engineers with practical guidance for selecting corrosion-resistant materials used in geothermal drilling and production systems.
  • TiCN-coated SS 18-8 offers improved durability that can reduce equipment replacement frequency and maintenance costs.
  • Enhanced corrosion resistance contributes to longer operational life for geothermal drilling tools and infrastructure.
  • The study demonstrates the industrial value of Physical Vapor Deposition as an effective surface engineering technology for harsh operating environments.
  • The integrated testing approach can assist manufacturers in evaluating protective coatings before industrial implementation.
  • The results may also benefit other industries operating under aggressive corrosive conditions, including oil and gas, marine engineering, chemical processing, and power generation.
  • Improved material durability supports more reliable geothermal energy production while reducing lifecycle costs and enhancing infrastructure sustainability.

Research Limitations

  • The experimental investigation was conducted using only two stainless steel substrates, namely ferritic SS 11-0 and austenitic SS 18-8. Consequently, the findings should not be generalized to all stainless steel grades without further validation.
  • Corrosion resistance was evaluated under laboratory-controlled neutral salt spray conditions using a 5% NaCl solution. Although this method simulates corrosive environments, it does not fully reproduce the chemical complexity of actual geothermal fluids containing dissolved gases, acidic species, and mineral deposits.
  • The coating process employed a single deposition technique—Physical Vapor Deposition (PVD)—under fixed operating conditions. The study did not compare alternative coating technologies or investigate the influence of other deposition parameters on corrosion performance.
  • Only three deposition durations (15, 25, and 35 minutes) were investigated. Other deposition times or coating thicknesses may produce different microstructural characteristics and corrosion behavior.
  • The research focused primarily on corrosion resistance, coating morphology, elemental composition, thickness, and hardness. Long-term mechanical performance, fatigue behavior, wear under operational loading, and thermal cycling were beyond the scope of the investigation.
  • Although FESEM observations identified coating defects such as pinholes and macroparticles, the study did not quantitatively evaluate their influence on long-term coating degradation under continuous geothermal service conditions.
  • The electrochemical measurements provided valuable information regarding corrosion kinetics; however, extended field validation under actual geothermal operating conditions was not performed.

Future Research Opportunities

  • Evaluate TiCN-coated stainless steels under actual geothermal field conditions to validate laboratory observations over extended operating periods.
  • Investigate the corrosion performance of TiCN coatings in geothermal fluids containing dissolved hydrogen sulfide, carbon dioxide, chloride-rich brines, and acidic environments representative of real geothermal reservoirs.
  • Optimize PVD processing parameters—including substrate temperature, chamber pressure, deposition power, and bias voltage—to further improve coating adhesion, density, and corrosion resistance.
  • Compare TiCN with other advanced ceramic coatings or multilayer coating systems to identify materials capable of providing superior long-term protection in geothermal applications.
  • Study the influence of coating defects such as pinholes, pores, and macroparticles on corrosion initiation, coating delamination, and long-term durability.
  • Investigate the combined effects of corrosion, wear, erosion, and thermal cycling to better represent the complex service conditions experienced by geothermal drilling components.
  • Develop predictive corrosion models that integrate electrochemical behavior, coating characteristics, and environmental variables to support material selection and lifetime prediction.
  • Assess the economic feasibility and lifecycle benefits of TiCN-coated stainless steels for large-scale geothermal infrastructure and industrial deployment.

Potential for Public Policy Citation

This research provides evidence that advanced surface engineering technologies can substantially improve the durability of metallic components used in geothermal energy systems. The findings are relevant to governmental agencies, energy regulators, and infrastructure planners seeking to improve the reliability and sustainability of renewable energy facilities.

The demonstrated performance of TiCN-coated austenitic stainless steel may support policies encouraging the adoption of corrosion-resistant materials for geothermal exploration, drilling, and power generation infrastructure. Improved material durability has the potential to reduce maintenance requirements, minimize equipment failures, enhance operational safety, and lower lifecycle costs.

The study may also inform future technical standards related to protective coatings, corrosion testing, and material qualification for aggressive industrial environments where long-term structural reliability is essential.

Who Should Read This Paper?

  • Materials scientists investigating corrosion-resistant metallic materials and protective ceramic coatings.
  • Corrosion engineers developing advanced surface engineering technologies for harsh environments.
  • Researchers specializing in Physical Vapor Deposition (PVD) and thin-film coating technologies.
  • Mechanical and manufacturing engineers involved in material selection for high-performance engineering components.
  • Geothermal engineers responsible for drilling equipment, pipelines, and power generation infrastructure.
  • Industrial practitioners seeking durable materials capable of operating under corrosive service conditions.
  • Graduate students and academic researchers studying corrosion science, surface engineering, and sustainable energy materials.
  • Decision-makers responsible for infrastructure maintenance, renewable energy investment, and materials qualification.

Final Thoughts

This study presents a comprehensive experimental comparison of TiCN-coated ferritic and austenitic stainless steels intended for geothermal engineering applications. By integrating microstructural characterization, hardness evaluation, accelerated corrosion testing, and electrochemical analysis, the research provides robust evidence regarding the influence of substrate composition on coating performance.

The experimental results consistently demonstrate that TiCN coatings significantly improve corrosion resistance for both stainless steel substrates. However, the superior chromium and nickel contents of austenitic SS 18-8 create a stronger passive protective layer that works synergistically with the TiCN coating, resulting in better corrosion resistance, improved surface quality, and enhanced mechanical performance than ferritic SS 11-0.

Beyond its immediate contribution to corrosion science, this work offers practical engineering guidance for selecting materials capable of operating reliably in aggressive geothermal environments. The findings reinforce the importance of combining appropriate substrate selection with advanced surface engineering techniques to improve equipment durability, reduce maintenance requirements, and support the long-term sustainability of geothermal energy systems.

Suggested Citations

Teknomekanik (UNP) Style

Solehudin, A., Salam, H., Permana, E., Noviyanti, A. R., Umar, A. A., & Ragadhita, R. (2026). Comparative study on the corrosion behavior of TiCN-coated austenitic and ferritic stainless steels in geothermal environments. Teknomekanik, 9(2), 137–161. https://doi.org/10.24036/teknomekanik.v9i2.44172

APA (7th Edition)

Solehudin, A., Salam, H., Permana, E., Noviyanti, A. R., Umar, A. A., & Ragadhita, R. (2026). Comparative study on the corrosion behavior of TiCN-coated austenitic and ferritic stainless steels in geothermal environments. Teknomekanik, 9(2), 137–161. https://doi.org/10.24036/teknomekanik.v9i2.44172

IEEE Style

A. Solehudin, H. Salam, E. Permana, A. R. Noviyanti, A. A. Umar, and R. Ragadhita, "Comparative study on the corrosion behavior of TiCN-coated austenitic and ferritic stainless steels in geothermal environments," Teknomekanik, vol. 9, no. 2, pp. 137–161, 2026, doi:10.24036/teknomekanik.v9i2.44172.

Harvard Style

Solehudin, A., Salam, H., Permana, E., Noviyanti, A.R., Umar, A.A. and Ragadhita, R., 2026. Comparative study on the corrosion behavior of TiCN-coated austenitic and ferritic stainless steels in geothermal environments. Teknomekanik, 9(2), pp.137–161. Available at: https://doi.org/10.24036/teknomekanik.v9i2.44172.

Vancouver Style

Solehudin A, Salam H, Permana E, Noviyanti AR, Umar AA, Ragadhita R. Comparative study on the corrosion behavior of TiCN-coated austenitic and ferritic stainless steels in geothermal environments. Teknomekanik. 2026;9(2):137–161. doi:10.24036/teknomekanik.v9i2.44172.

Chicago (Author–Date)

Solehudin, Agus, Haipan Salam, Enda Permana, Atiek Rostika Noviyanti, Akrajas Ali Umar, and Risti Ragadhita. 2026. "Comparative Study on the Corrosion Behavior of TiCN-Coated Austenitic and Ferritic Stainless Steels in Geothermal Environments." Teknomekanik 9 (2): 137–161. https://doi.org/10.24036/teknomekanik.v9i2.44172.

MLA (9th Edition)

Solehudin, Agus, et al. "Comparative Study on the Corrosion Behavior of TiCN-Coated Austenitic and Ferritic Stainless Steels in Geothermal Environments." Teknomekanik, vol. 9, no. 2, 2026, pp. 137–161. https://doi.org/10.24036/teknomekanik.v9i2.44172.

Editorial Note

This article review is prepared for Engineering Research Insights based exclusively on the published research article and is intended to provide readers with an accessible scientific overview without replacing the original publication. The bibliographic metadata have been verified using the official journal webpage, while the scientific analysis is derived solely from the published article. Readers are encouraged to consult the original paper for complete experimental procedures, datasets, figures, and technical discussions.

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