Corrosion of marine beach piers

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Corrosion of marine beach piers is a structural degradation phenomenon caused by the combined effects of electrochemical, physical, and biological factors in high-salt, oxygen-rich marine environments; it significantly reduces the service life of these facilities, resulting in economic losses of hundreds of billions of yuan in China each year. I. Main causes of corrosion: Electrochemical processes play a key role. Seawater is a strong electrolyte containing 3% to 3.5% sodium chloride; chloride ions destroy the passivation layer on the metal surface, accelerating the electrochemical reaction process, which is the primary cause of corrosion. Differences in environmental zones: The marine corrosion environment surrounding the dock is divided into 5 zones. In the splash zone, where there is a constant alternation between wet and dry conditions along with an adequate supply of oxygen, the corrosion rate can be 5 to 10 times higher than that in the fully submerged zone; this makes it the most corrosive area. Biological factor accumulation: Microorganisms such as sulfate-reducing bacteria form biofilms on metal surfaces, producing corrosive substances through their metabolism; approximately 20% of marine corrosion losses are caused by microbial corrosion. Accelerated by physical effects: The continuous action of waves and tides erodes the protective layer, carrying away the corrosion products, thus creating a vicious cycle of \"erosion-corrosion\". II. Common types of corrosion
Uniform corrosion: The entire metal surface is eroded at a similar rate, resulting in a uniform reduction in its overall thickness. Local corrosion: includes pitting corrosion, crevice corrosion, galvanic corrosion, etc. Among these, pitting corrosion penetrates deep into the metal, and can easily lead to structural failure due to perforation. Microbial corrosion: Driven by the metabolic activities of marine microbial communities, it is the main cause of unknown punctate perforations in dock structures. Corrosion fatigue: The premature fracture and failure of metal structures under the cyclic action of waves.