Etching of aluminum alloy parts before oxidation

Etching is the first process before oxidation of aluminum and aluminum alloy parts, and it is also one of the key steps to ensure the quality of oxide film   In order to ensure the etching quality, a series of pre-treatment should be carried out before etching In addition to removing all impurities that cannot react with alkaline solution or can react with chemical solution, but will seriously affect the surface quality of the parts, organic solvent cleaning or weak alkali containing surfactant should be carried out according to the degree of oil contamination on the surface of the parts Pretreatment is carried out in sexual solution to remove thick oil and other dirt Etching is not only the process of removing oil thoroughly, but also the process of removing oxide film Therefore, all processes before and after etching need to be closely coordinated, and cleaning with a single organic solvent or in a weak alkaline solution can not meet the requirements of the process of removing oil stains on the surface of the parts If the strong alkali etching treatment is carried out directly on this part, it will be blocked by the uneven oil on the surface, and the etching solution will not react synchronously on the surface of the aluminum part, so the surface will be damaged and react In serious cases, there may also be potholes and inequalities, which will seriously affect the appearance of the product, and at the same time, it will also bring quality defects such as tolerance and fit The lighter will be repaired and the heavier will be It is scrapped However, these processes are not always required before strong alkali etching, but also depend on the surface condition of the parts: the parts with good surface condition and without serious oil stain can be directly etched in strong alkali solution After etching, in order to remove the ash and alkaline substances which are difficult to wash, it is necessary to carry out light (also known as neutralization) treatment So as to achieve a clean surface, so that the surface of the part is completely exposed, so as to ensure that the solution of the next process is not polluted, and lay the foundation for obtaining a normal oxide film The steps that need to be taken in the whole process of etching treatment are: ① remove the adherent on the surface of the parts; ② clean with organic solvent; ③ chemical cleaning; ④ alkali etching; ⑤ light out The technical requirements, operation points and precautions in the above processes are systematically discussed in the questions and answers in the following sections