Tribology and Materials | Volume 5 | Issue 1 | 2026 | 22-30
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https://doi.org/10.46793/tribomat.2026.005
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Anodic and chrome coatings for firearm barrels: Microstructural and phase analysis
Veselina Dimitrova
1,
Ventsislav Dimitrov
1,
Galya Zdravcheva2
1 Faculty of Engineering and Pedagogy of Sliven, Technical University of Sofia, Sliven, Bulgaria
2 Technical College − Sofia, Technical University of Sofia, Sofia, Bulgaria
Abstract: The study employs X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) and metallographic analysis to assess the phase composition and microstructural features of anodic and chrome coatings. In response to increasing demands for enhanced durability and corrosion resistance in defence applications, surface treatments have become an integral part of the barrel manufacturing process. Aluminium barrels were anodised, while steel barrels were hard chrome plated. The electrochemical rifling (ECR) process was conducted under optimised conditions: current ≈ 950 A, voltage ≈ 7 V, pressure ≈ 2.2 MPa and duration ≈ 176 s. Before coating deposition, the inner bore surface roughness was controlled at Ra = 0.8 µm, ensuring reliable adhesion of the subsequent layers. The XRD and EDS results confirmed near-stoichiometric compositions for both coating types. The anodised layers revealed aluminium and γ-Al2O3 phases, accompanied by minor intermetallic compounds, such as S (Al2CuMg), T (Al2Mg3Zn3) and η (MgZn2). Chrome-plated steel sample exhibited the presence of elemental chromium and goethite (β-FeOOH). These findings support the suitability of the ECR method as a foundation for high-performance coating systems in military applications.
Keywords: electrochemical rifling, firearm barrel, chromium coatings, aluminium oxide, XRD, EDS, surface characterisation, military coatings.
Received: 01-09-2025, Revised: 08-10-2025, Accepted: 29-11-2025
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license, which allows users to distribute, remix, adapt,
and build upon the material in any medium or format for non-commercial purposes only, and only so long as attribution is given to the creator.
2 Technical College − Sofia, Technical University of Sofia, Sofia, Bulgaria
Abstract: The study employs X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) and metallographic analysis to assess the phase composition and microstructural features of anodic and chrome coatings. In response to increasing demands for enhanced durability and corrosion resistance in defence applications, surface treatments have become an integral part of the barrel manufacturing process. Aluminium barrels were anodised, while steel barrels were hard chrome plated. The electrochemical rifling (ECR) process was conducted under optimised conditions: current ≈ 950 A, voltage ≈ 7 V, pressure ≈ 2.2 MPa and duration ≈ 176 s. Before coating deposition, the inner bore surface roughness was controlled at Ra = 0.8 µm, ensuring reliable adhesion of the subsequent layers. The XRD and EDS results confirmed near-stoichiometric compositions for both coating types. The anodised layers revealed aluminium and γ-Al2O3 phases, accompanied by minor intermetallic compounds, such as S (Al2CuMg), T (Al2Mg3Zn3) and η (MgZn2). Chrome-plated steel sample exhibited the presence of elemental chromium and goethite (β-FeOOH). These findings support the suitability of the ECR method as a foundation for high-performance coating systems in military applications.
Keywords: electrochemical rifling, firearm barrel, chromium coatings, aluminium oxide, XRD, EDS, surface characterisation, military coatings.
Received: 01-09-2025, Revised: 08-10-2025, Accepted: 29-11-2025
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This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license, which allows users to distribute, remix, adapt, and build upon the material in any medium or format for non-commercial purposes only, and only so long as attribution is given to the creator.