Cailiao Baohu (Oct 2023)
Study on Salt Spray Corrosion and Decay of Mechanical Properties of Steels for Substation Facilities and 7xxx Aluminum Alloy
Abstract
The corrosion failure of steel is one of the key problems to shorten the service life of power facilities in some strong corrosive environments， such as marine and chemical plants.To address this problem， the proposition of substituting steel in power transmission and transformation equipment with high-strength 7xxx series aluminum alloys was introduced.Accelerated indoor simulation tests were conducted， using a 5%NaCl salt spray corrosion environment to emulate marine atmospheric conditions.A comparative analysis was performed on the mechanical property degradation and change law of surface corrosion morphology of Q345 steel for substation facilities and 7075 aluminum alloy after varying corrosion durations (7，21，42 d) by integrating tensile tests and microscopic structural observations.Further， employing corrosion weight loss methods and computer simulation techniques， the mechanical properties of the two materials under identical corrosion conditions and loads were comparatively studied.Results indicated that the mechanical properties of both materials tended to decline with the extension of salt spray corrosion time under 5%NaCl salt spray corrosion environment， moreover， the highest tensile strength attenuation rate of Q345 steel (24.58%) was 8 times that of 7075 aluminum alloy (3.00%).Both materials displayed a corrosion rate trend that initially increased and then decreased， with the average corrosion rate of Q345 steel [0.03 g/(m2·d)] being approximately 15 times that of the 7075 aluminum alloy [0.002 g/(m2·d)].At the same corrosion cycle， the corrosion pits in Q345 steel were larger and deeper than those in the 7075 aluminum alloy， resulting in a significantly higher degree of stress concentration caused by corrosion pits in Q345 steel under the same external load compared to 7075 aluminum alloy.Consequently， in theory，7075 aluminum alloy could replace Q345 steel as the base material for power facility components.
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