Intergranular corrosion is a common corrosion phenomenon in localized corrosion and pitting corrosion of aluminum alloy. The corrosion occurs along the grain boundary or near it, so it is called intergranular corrosion. The cause of intergranular corrosion is generally believed to be caused by the potential difference between grain boundaries and adjacent grains. Taking AI-Cu-Mg alloy as an example, the grain boundary has a precipitate free zone after aging, which contains less Cu and more negative potential. The Cu is higher and the potential is positive. In the process of decay, Cu depleted zone the negative potential will be corrosion, and with aluminum dissolution, grain in isolated Cu also in solution, especially the Cu phase dissolved aluminum cathode directly into the solution, generating Cu2 ten. Because the redox potential of Cu2+ is very positive (relative to the potential of aluminum), it will be reduced in the cathode region of the aluminum surface, which is called the two precipitation.

As a result of this two precipitation behavior, the aluminum in the corrosive medium and the formation of a new rich Cu cathode phase, so that the corrosion process repeated. This phenomenon should be avoided in the protection of aluminum. However, in the surface etching of aluminum alloy, intergranular corrosion is another cause of texture, especially the material with acicular grain structure is more important for the formation of filamentary texture. In order to achieve this goal, we can add a proper amount of redox potential positive metal ions or oxidizing anions in the corrosion medium, so as to achieve the purpose of strengthening the etching of the aluminum alloy surface. But this can only have a significant effect on the alloy material with the tendency of filiform corrosion. It is also reported that in the electrolyte solution with inhibitor, the effect of the applied electric field on the surface of aluminum alloy is etched.

It is found that the effect of the alloy is not obvious, which is not to have the corrosion tendency of the filiform texture, and it is necessary to study further in order to be used in mass production. In the etching process, due to the potential difference, it is possible to etch along the boundaries of the grain, and then the whole grain is etched and dissolved. Therefore, it is easier to obtain high roughness texture effect on the grain size of the material. However, the large grain size will affect the strength of the material after etching, especially after a long time of etching, the greater the degree of influence. Therefore, it is very important to control the etching time (i.e., to control the amount of etching of the material) in the process of etching.