Corrosion Behavior and Mechanism of Gun Barrel Material in the Marine Atmospheric Environment

The importance of reliable and stable operation of equipment and materials，which directly serves equipment development and combat effectiveness generation，cannot be ignored.Firearms are among the most basic and widely used weapons，and their importance is self-evident given their high frequency of use and broad deployment.Numerous examples show that improper storage，inadequate protective maintenance，and limited corrosion-protection measures can lead to rusting or damage of firearms.However，existing research largely focuses on verifying whether the corrosion resistance of materials meets specifications，lacking a systematic analysis of the corrosion behavior and mechanisms of gun barrel materials in simulated marine atmospheric environments.Therefore，this study aimed to investigate the corrosion behavior and intrinsic mechanisms of a specific gun barrel material in a marine atmospheric environment by integrating multiple experimental methods，thereby providing theoretical support for developing targeted corrosion-mitigation technologies for such materials.To achieve the research objectives，a combination of experimental methods was employed.First，salt spray tests (compliant with the GB/T 10125－2021 standard，using 5%NaCl solution，pH 6.5－7.2) were conducted to simulate the marine atmospheric environment and accelerate the corrosion process.Second，corrosion electrochemical analysis was performed using a custom-made double-comb planar electrode (with an electrode spacing of 100 μm and a working area of 1 cm2)，and electrochemical impedance spectroscopy (frequency range:10－2－105 Hz) was measured to analyze the electrochemical reaction resistance.Third，the weight loss method was utilized: an electronic balance (0.1 mg precision) was used to weigh the gun barrel material specimens (dimensions:φ10 mm×2 mm) before and after corrosion to calculate the average corrosion rate.Fourth，Fourier Transform Infrared Spectroscopy (FT-IR，resolution 4 cm－1，scanning range 4 000－400 cm－1) was utilized to identify the types of corrosion products.Finally，the cross-sectional microstructure of the corrosion product layer was observed via Scanning Electron Microscopy (SEM，accelerating voltage 15 kV).The salt spray test results indicated that during the short-term corrosion process (7 d)，the corrosion rate of the gun barrel material remained essentially stable，with no significant acceleration or inhibition.The average corrosion rate was approximately 1.40 mm/a，and the generated corrosion products were loose and porous，providing limited protective effects to the substrate.FT-IR analysis confirmed that the primary corrosion products were γ-FeOOH，β-FeOOH，and δ-FeOOH.Electrochemical test results from the custom double-comb planar electrode showed that as the temperature increased (from 30 ℃ to 80 ℃)，the low-frequency impedance of the electrode decreased from 108 Ω·cm2 to 105 Ω·cm2，indicating a gradual increase in the corrosion rate.When the relative humidity (RH) increased from 50%to 70%，the low-frequency impedance significantly decreased (from 109 Ω·cm2 to 107 Ω·cm2)，corresponding to a higher corrosion rate.When the RH further increased from 70%to 90%，the Bode plots of the specimens at 90%RH exhibited two time constants，and the low-frequency impedance remained basically consistent with that at 80%RH (maintained around 107 Ω·cm2).This phenomenon was attributed to the formation of a continuous corrosion product film on the electrode surface at this humidity，which provided a certain degree of physical isolation.FT-IR analysis also revealed the evolution law of corrosion products: in the early stage of corrosion (within 1 d)，the surface corrosion products were mainly composed of γ-FeOOH and β-FeOOH.As the corrosion time extended from 2 d to 7 d，the intensity of the characteristic stretching vibration peaks of γ-FeOOH and β-FeOOH gradually increased，indicating the continuous accumulation of corrosion products.Meanwhile，δ-FeOOH gradually appeared in the corrosion products，and its content increased slightly with the extension of corrosion time.SEM observations further confirmed that the corrosion product layer was loose and contained numerous micro-cracks，which failed to effectively prevent the penetration of corrosive media (such as Cl－) into the substrate.This study systematically revealed the corrosion behavior and mechanisms of the gun barrel material in a simulated marine atmospheric environment.The results confirmed that temperature and relative humidity were key factors affecting the corrosion of the material: the corrosion tendency increased with rising temperature，and the charge transfer resistance (Rct)decreased (from 109 Ω·cm2 to 107 Ω·cm2) as the relative humidity increased (RH ＝50%－90%)，thereby leading to an increased corrosion rate.During the short-term corrosion process，the average corrosion rate of the material was stably maintained at approximately 1.40 mm/a，and the generated corrosion products (γ-FeOOH，β-FeOOH，δ-FeOOH) were loose and porous，offering limited protection to the substrate.These findings clarified the corrosion laws of the gun barrel material in a marine atmospheric environment and laid a foundation for the subsequent development of targeted anti-corrosion measures (such as surface coating modification).