Aluminum application knowledge

Point corrosion

       Pitting corrosion, also known as pore corrosion, is a localized corrosion pattern that produces pinpoints, spots, and holes on a metal. Pitting corrosion is a unique form of anodic reaction and is an autocatalytic process in which the conditions caused by the corrosion process within the pitting hole continue to maintain corrosion.

2. Uniform corrosion

       In a solution of aluminum phosphate such as phosphoric acid and sodium hydroxide, the oxide film thereon is dissolved, uniform corrosion occurs, and the dissolution rate is uniform. The temperature of the solution rises and the concentration of the solute is large, which promotes the corrosion of aluminum.

3. Crevice corrosion

       Crevice corrosion is a type of localized corrosion. In the electrolyte solution, the metal is interposed between the metal or the metal and the non-metal, and the width thereof causes the medium to immerse and the medium is in a stagnant state, so that the corrosion inside the gap is intensified, which is called crevice corrosion.

4. Stress corrosion cracking (SCC)

       The SCC of aluminum alloy was discovered in the early 1930s. A type of failure of a metal under the combined action of stress (tensile or internal stress) and corrosive media is called SCC. SCC is characterized by the formation of corrosion-mechanical cracks that can develop along grain boundaries or through grain extension. Since the crack propagation is inside the metal, the strength of the metal structure is greatly reduced, and sudden damage occurs in severe cases. SCC occurs under certain conditions, which are: tensile stress or residual stress inside the metal.