After being placed for a while, the surface of aluminum castings will appear signs of corrosion. Why does aluminum casting turn white and rust? How to prevent and reduce corrosion or rust of aluminum parts?
Generally speaking, aluminum may form a layer of aluminum oxide protective film on its surface, which can play a role of rust and corrosion protection on the surface of aluminum parts. Therefore, if aluminum parts are stored in general environment, rust and oxidation will not occur if there is no sudden change in the environment. If the cutting fluid with different concentration is used in the processing of aluminum castings, or there are factors harmful to aluminum products in the composition, corrosion and oxidation will also occur, and the oxide film on the surface of aluminum castings is not a pure anti-corrosion aluminum oxide protective film.
During the processing of aluminum parts, each process should be thoroughly cleaned to remove the residual cutting fluid and grinding fluid, so as to avoid long-term corrosion on the surface of aluminum parts.
No matter which cleaning agent is used to clean the oil stain on the aluminum surface, the following points should be noted:
– Clean the oil and other dirt on the surface with industrial cleaning agent first.
– Then rinse with clean water to ensure that the aluminum surface is free of detergent residue and dust.
– After cleaning, the surface should be inspected for cleanliness, and painting should be carried out after meeting the requirements.
– After cleaning, drying or airing is required, as well as drying and cooling of the surface. This process also needs to control the pollution caused by the operating environment.
– During the cleaning and drying process, the operator should take protective measures, and should not directly touch the workpiece with hands to avoid sweat pollution.
However, if aluminum castings or aluminum alloy parts are transported, especially in the environment of sea transportation and great changes in temperature and humidity, aluminum is relatively easy to be corroded, which will result in the formation of aluminum salts and hydroxides, that is, the so-called white hairs on the surface of aluminum parts. In addition, if wooden cases are selected for direct packaging and transportation of aluminum castings, wooden cases are prone to produce lignic acid and corrosion in humid air.
How to prevent or reduce corrosion of aluminum parts:
1) The use concentration of cutting fluid should be controlled, and the composition of cutting fluid should be tested regularly to ensure that the composition is within the effective use range and there is no damage to the surface of aluminum parts.
2) For the cleaning of each process of aluminum manufacturing, environment-friendly metal cleaner with strong cleaning ability can be selected to clean the cutting fluid and other oil stains and dirt on the aluminum surface in a timely manner, and rinsing is required to remove the residual metal cleaner
3) For the transportation of aluminum parts, do not directly use wooden boxes or cartons for contact packaging. Instead, use anti rust bags with low water permeability and anti rust effect for direct packaging. The external packaging can use cardboard boxes, wooden boxes or other fixed packaging. In addition, in order to ensure that the humidity in the package will not cause corrosion and oxidation risk to aluminum parts, moisture-proof desiccant bags can be placed in the package to increase transportation protection.