The following are some factors that will accelerate the corrosion of aluminum sheet:
A high - humidity environment is one of the important factors accelerating the corrosion of aluminum sheets. When the relative humidity in the air exceeds a certain level (usually about 60%), a thin water film will form on the surface of the aluminum sheet. Various corrosive substances, such as oxygen, carbon dioxide, sulfur dioxide, etc., may be dissolved in the water. These substances react chemically with aluminum, leading to the corrosion of the aluminum sheet. For example, in coastal areas or regions with a long rainy season, the high - humidity environment makes the aluminum sheet more susceptible to corrosion.
Aluminum is prone to corrosion in both acidic and alkaline environments. In an acidic environment, hydrogen ions react with aluminum to produce aluminum ions and hydrogen gas. For example, in an industrial environment, if aluminum sheet comes into contact with acidic gases (such as sulfur dioxide, hydrogen chloride, etc.) or acidic liquids (such as sulfuric acid, hydrochloric acid, etc.), the corrosion will be accelerated. In an alkaline environment, hydroxide ions also react with aluminum to produce aluminate and hydrogen gas. For example, in some environments containing alkaline substances, such as cement, lime, etc., the aluminum sheet is also prone to corrosion.
In coastal areas or marine environments, the air contains a large amount of salt, forming salt spray. Chloride ions in the salt spray can accelerate the corrosion of aluminum sheets. Chloride ions have a strong penetrating ability and can damage the oxide film on the surface of the aluminum sheet, exposing the aluminum to a corrosive environment and thus accelerating corrosion. For example, the aluminum sheets used on offshore oil platforms, ships and other facilities are vulnerable to the erosion of salt spray.
An increase in temperature accelerates the corrosion rate of aluminum sheets. On the one hand, a rise in temperature speeds up the chemical reaction rate, thus accelerating the reaction between aluminum and corrosive substances. On the other hand, a high - temperature environment makes the oxide film on the surface of the aluminum sheet unstable and prone to cracking, thus losing its protective effect on aluminum. For example, in high - temperature industrial environments such as refineries and chemical plants, the corrosion rate of aluminum sheets will increase significantly.
During the transportation, installation, and use of aluminum sheets, if they are subject to mechanical damage such as scratches and collisions, the oxide film on their surface will be damaged, exposing the aluminum to the air and thus accelerating corrosion. For example, during the construction process, accidentally scratching the surface of the aluminum sheet, or colliding with sharp objects during handling, may cause corrosion of the aluminum sheet.
If the aluminum sheet is cleaned with inappropriate cleaning agents or methods, it may also accelerate corrosion. For example, using acidic or alkaline cleaning agents to clean the aluminum sheet will damage the oxide film on its surface; using rough cleaning tools such as wire brushes will scratch the surface of the aluminum sheet, thus accelerating corrosion.
During the welding process of aluminum sheets, if the welding process is improper, such as too high welding temperature or too long welding time, the oxide film on the surface of the aluminum sheet will be damaged, and at the same time, welding defects such as pores and cracks may occur, which will accelerate the corrosion of the aluminum sheet. For example, in some steel structure projects, if the welding parts between the aluminum sheet and the steel structure are not properly treated, corrosion problems are likely to occur.
The impurity content in aluminum sheets can affect their corrosion resistance. If the aluminum sheet contains a relatively high amount of impurities such as iron, copper, and silicon, these impurities will form a galvanic cell with aluminum, accelerating the corrosion of aluminum. For example, some low - quality aluminum sheets, due to impure raw materials and a high impurity content, are prone to corrosion.
Different aluminum alloy compositions also have different sensitivities to corrosion. Some aluminum alloys containing specific alloying elements, such as magnesium, zinc, etc., may accelerate corrosion in specific environments. For example, some high-strength aluminum alloys are prone to stress corrosion cracking in a humid environment.
The surface treatment quality of aluminum sheet is crucial to its corrosion resistance. If the surface treatment is incomplete, such as uneven thickness of the oxide film and poor coating adhesion, the aluminum sheet will be more prone to corrosion. For example, the surface treatment process of some low - cost aluminum sheets is simple, and the coating quality is poor, which easily leads to problems such as peeling and blistering, thus accelerating corrosion.
