Influence of ultraviolet rays: Ultraviolet rays in outdoor environments are one of the important factors that cause aging of the galvanized layer. Ultraviolet rays have high energy and can destroy the chemical bonds on the surface of the galvanized layer. Long-term exposure will change the molecular structure of the surface of the zinc layer, resulting in a decrease in its glossiness and a gradual roughening of the surface. This not only affects the appearance of metal products, but may also reduce the protective performance of the coating.
Rainwater erosion: The erosion of rainwater will continuously wear the galvanized layer. Rainwater contains a certain amount of acidic substances, such as carbonic acid and sulfurous acid formed by the dissolution of carbon dioxide and sulfur dioxide. These acidic substances will react chemically with zinc and gradually dissolve the zinc layer. Especially in acid rain areas, this erosion effect is more obvious. As time goes by, the thickness of the galvanized layer gradually decreases, and its ability to protect the base metal is also weakened.
Temperature changes: The temperature difference between day and night and the temperature fluctuations caused by seasonal changes will cause thermal expansion and contraction in galvanized metal products processing. Due to the different thermal expansion coefficients of zinc and base metal, stress will be generated between the galvanized layer and the base metal during repeated thermal expansion and contraction. This stress may cause cracks or even fall off in the galvanized layer, thus accelerating the aging of the coating.
Humidity effect: A high humidity environment provides favorable conditions for chemical reactions. In humid air, zinc is prone to electrochemical corrosion. Water molecules form a thin layer of water film on the surface of the galvanized layer. This water film works together with substances such as oxygen and carbon dioxide in the air to oxidize zinc and generate corrosion products such as zinc hydroxide. These products accumulate on the surface of the galvanized layer, affecting its protective properties.
Effect of atmospheric pollutants: Pollutants emitted by industrial waste gas, automobile exhaust, etc., such as chlorides and sulfides, will react chemically with the galvanized layer. For example, chlorides will accelerate the corrosion of zinc, forming soluble salts such as zinc chloride, resulting in rapid loss of the galvanized layer. The presence of these pollutants greatly reduces the weather resistance of the galvanized layer and shortens its service life.
Microbial erosion: In outdoor environments, some microorganisms such as algae and fungi may grow and reproduce on the surface of galvanized metal products processing. These microorganisms secrete acidic substances during their growth, which corrode the galvanized layer. In addition, the attachment of microorganisms will also affect the air permeability and humidity distribution of the galvanized layer surface, further accelerating the aging process.
Summary of aging mechanism: The aging of the coating of galvanized metal products processing in outdoor environments is the result of the combined effect of multiple factors. Ultraviolet rays destroy the molecular structure, rain, humidity and atmospheric pollutants cause chemical corrosion, temperature changes produce stress damage, and microbial erosion accelerates this process from a biochemical perspective. Understanding these weather resistance and aging mechanisms will help take targeted protective measures to extend the service life of galvanized metal products processing outdoors.
