Multi-stage Pitting Evolution of 7075 Aluminum Alloy in a Hot-humid Marine Atmosphere and Analysis Using an Improved Weibull Damage Kinetics Model

LIU Zhiguo; SUN Chenglong; SUN Dehai; HOU Wang; WU Nana

doi:10.7643/ issn.1672-9242.2026.02.012

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Equipment Environmental Engineering ›› 2026, Vol. 23 ›› Issue (2) : 103-113. DOI: 10.7643/ issn.1672-9242.2026.02.012

船舶及海洋工程装备Ships and Marine Engineering Equipment

Multi-stage Pitting Evolution of 7075 Aluminum Alloy in a Hot-humid Marine Atmosphere and Analysis Using an Improved Weibull Damage Kinetics Model

LIU Zhiguo¹, SUN Chenglong^1,2, SUN Dehai³, HOU Wang⁴, WU Nana⁵

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Abstract

The work aims to reveal the multi-stage evolutionof corrosion pits on 7075aluminum alloy subjectto a hot and humid Marine atmospheric environment and establish a dynamic prediction model for corrosion damage. A cyclic accelerated corrosion test scheme simulating the South China Sea environment was designed and implemented, and the corrosion process was accelerated through the alternating impregnation method. The three-dimensional topography parameters such as the projected area, depth and volume of corrosion pits under different equivalent service lives (3 to 13 years) were obtained with a super-depth-of-field three-dimensional microscope. On this basis, a modified Weibull dynamic model was proposed and applied to fit the corrosion evolution law in stages.The results delineated a clear triphasic evolution mechanism. Theinitial stage (3-7 years) was dominated by pit deepening, with an average annual depth increase of 4.8 μm and a high aspect ratio of 1.3. Theintermediate stage (7-11 years)witnessed a paradigm shift to accelerated lateral expansion, governed by autocatalytic effects within the pit. The pit area growth rate surged to an annual average of 3.4×10⁴ μm², and the morphology transitioned from narrow-deep to a near-spherical shape (aspect ratio ≈1.0). In thelate stage (11-13 years), growth saturation occurred due to the physical blockage by accumulated corrosion products, resulting in a bowl-shaped morphology (aspect ratio≈0.8).Themodified Weibull model canaccurately describe the dynamic behavior and transition nodes at each stage. The phased transformation of the corrosion pit on 7075 aluminum alloy from deepening to lateral expansion is mainly regulated by the repeated cracking of the passivation film and the subsequent autocatalytic corrosion process. The established “three-dimensional morphology of corrosion-dynamics” correlation mechanism provides a theoretical basis and quantitative tool for the life prediction and critical damage assessment of high-strength aluminum alloy serving in marine environments.

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7075 aluminum alloy / wet/dry cyclic corrosion test / marine atmospheric corrosion / corrosion pit evolution / Weibull model / kinetic analysis

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LIU Zhiguo, SUN Chenglong, SUN Dehai, HOU Wang, WU Nana. Multi-stage Pitting Evolution of 7075 Aluminum Alloy in a Hot-humid Marine Atmosphere and Analysis Using an Improved Weibull Damage Kinetics Model[J]. Equipment Environmental Engineering. 2026, 23(2): 103-113 https://doi.org/10.7643/ issn.1672-9242.2026.02.012

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