1. Pitting corrosion
Pitting corrosion, also known as hole corrosion, is a localized form of corrosion that produces pinpoint, point, and hole shapes on metals. Pitting corrosion is a unique form of anodic reaction, which is an autocatalytic process, that is, the conditions caused by the corrosion process in the pitting pores maintain the continuation of corrosion.
2. Uniform corrosion
In the solution of phosphoric acid and sodium hydroxide, the oxide film on it will dissolve, and uniform corrosion will occur, and the dissolution rate is also uniform. The temperature of the solution increases and the solute concentration increases, which promotes the corrosion of aluminum.
3. Crevice corrosion
Crevice corrosion is a localized corrosion. In the electrolyte solution of metal parts, due to the formation of gaps between metals and metals or between metals and non-metals, the width of the gap makes the medium immersed and the medium is in a stagnant state, which makes the internal corrosion of the crevice aggravated. The phenomenon is called crevice corrosion.
4. Stress Corrosion Cracking (SCC)
SCC of aluminum alloys was discovered in the early 1930s. A kind of damage that occurs in metal under the combined action of stress (tensile stress or internal stress) and corrosive medium, which is called SCC. SCC is characterized by the formation of corrosion-mechanical cracks that can either develop along grain boundaries or propagate through grains. Since the crack propagation is inside the metal, the strength of the metal structure will be greatly reduced, and sudden damage will occur in severe cases. SCC occurs under certain conditions, they are: tensile stress or residual stress inside the metal.