Aluminum processed by Dalian auto parts belongs to amphoteric metal, which will cause corrosion to varying degrees in the presence of acid or alkali. In particular, aluminum alloy castings have more pores, and the components also contain silicon and several heavy metals. Their corrosion resistance is worse than other aluminum alloys. Aluminum castings without protective treatment will be corroded and produce white rust as long as they encounter slightly alkaline or acidic water, or even rain, moisture, dew, etc.

Solutions.

After the aluminum casting is completed, the surface pretreatment shall be carried out before machining. For example, the casting shall be sandblasted in advance and coated with a layer of primer (such as zinc chrome yellow primer), and then machining shall be carried out on this basis, so as to avoid corrosion of the aluminum casting without protection.

Aluminum, silver white light metal. It has ductility. Commodities are often made into rod, sheet, foil, powder, ribbon and filament. It can form an oxide film to prevent metal corrosion in humid air. Aluminum powder can burn violently when heated in the air and emit a dazzling white flame. It is easily soluble in dilute sulfuric acid, nitric acid, hydrochloric acid, sodium hydroxide and potassium hydroxide solutions, but hardly soluble in water. The relative density is 2.70. Melting point 660 ℃. Boiling point 2327 ℃. Aluminum is the most abundant metal element in the earth's crust, ranking third only to oxygen and silicon. The development of three important industries, aviation, construction and automobile, requires that the material properties have the unique properties of aluminum and its alloys, which is greatly conducive to the production and application of this new metal aluminum.

It is widely used. Aluminum is an active metal. In dry air, a dense oxide film with a thickness of about 50 angstroms (1 angstrom =0.1 nm) is immediately formed on the surface of aluminum, so that aluminum will not be further oxidized and can resist water; However, aluminum powder is very easy to burn when mixed with air; Molten aluminum is a metal that can react violently with water; Aluminum is amphoteric, very soluble in strong alkali, but also soluble in dilute acid. According to the reducibility of aluminum, it can be inferred that aluminum can react with water. However, the experiment found that there is almost no reaction between aluminum and boiling water. However, aluminum can react significantly with water vapor under heating conditions, but a dense oxide film is formed with oxygen in water at the beginning of the reaction to prevent the further reaction. Aluminum is silver white light metal.

It has ductility. Commodities are often made into columns, rods, sheets, foils, powders, strips and filaments. It can form an oxide film to prevent metal corrosion in humid air. The aluminum powder treated with acid can burn violently when heated in air and emit dazzling white flame. Soluble in dilute sulfuric acid, dilute nitric acid, hydrochloric acid, sodium hydroxide and potassium hydroxide solutions, insoluble in water, but can slowly react with hot water to form aluminum hydroxide, with a relative density of 2.70, an elastic modulus of 70gpa and a Poisson's ratio of 0.33. Melting point 660 ℃. Boiling point 2327 ℃. It is widely used for its light weight, good electrical and thermal conductivity, high reflectivity and oxidation resistance. Aluminum used for daily utensils is usually called "steel" or "steel". The thermal expansion coefficient of Al at (room temperature) 25 ℃ is 0.0000236mm/ ℃ or 23.6ppm*k-1.