Corrosion mechanism of aviation aluminum alloy during machining process

Corrosion of aviation aluminum alloy parts during machining is a common and difficult problem, which is directly related to long-term immersion in cutting fluid. In this paper, immersion experiments with cutting fluid were applied to simulate the corrosion phenomenon of aviation aluminum alloy parts in the machining process. Taking other auxiliary experiments into account, the corrosion mechanism of aviation aluminum alloy parts in machining process was analyzed. The content of Al, Mg, Zn, and Cu elements in corrosion area decreased significantly, the content of C and O elements increased significantly. In detail, the dissolution of aluminum matrix and alloy elements was related to the impurity composition of cutting fluid. A high content of chloride ion (Cl⁻) in used cutting fluid was highly corrosive to aviation aluminum alloy parts. A high content of calcium ion (Ca²⁺), magnesium ion (Mg²⁺) and sodium ion (Na⁺) in used cutting fluid can indirectly accelerate the corrosion of aviation aluminum alloy. In addition, these impurity ions improved the conductivity of used cutting fluid, thus accelerating the electrochemical corrosion of aviation aluminum alloy. Meanwhile, corrosion inhibitor in used cutting fluid could be consumed by the impurity ions, thus weakening protective effect of corrosion inhibitor. This paper provided a theoretical basis for protection of aviation aluminum alloy parts in machining process, research of cutting fluid corrosion inhibitor.