The precision casting industry is developing faster and faster, and the use of precision castings is also increasing, so there are many more issues to consider when processing precision castings.

     Generally include degreasing and derusting activation, two processes, the quality of pretreatment is the key to the success or failure of normal temperature blackening, that is, the degreasing must be thorough, and the surface activation must be moderate (that is, the fresh metal surface is exposed without excessive corrosion). Pay attention to the following three points for castings:

    1. First soak or wash with clean water. Before chemical degreasing and rust removal of the workpiece, the workpiece is cleaned (soaked). One is to clean the workpiece first, and the other is to fill the surface of the workpiece with water to facilitate cleaning after chemical treatment.

    2. Use mechanical method to remove oxide scale. Such as: rolling, sandblasting, polishing, polishing, etc. Some castings are treated by this method, and then washed with water, they can be directly blackened or treated with other anti-rust treatments.

    3. Degreasing and derusting activation. Due to the large number of pores on the surface of castings, it is difficult to remove pollution, especially oil stains. Poor treatment will affect the entire anti-rust treatment and fail to achieve the expected purpose, including iron, copper, aluminum, etc. and their alloys Castings.

    There are many ways to remove oil. Such as: chemical degreasing, mechanical degreasing, baking degreasing, ultrasonic degreasing, electrolysis and organic solvent degreasing, etc. Derusting activation generally adopts hydrochloric acid solution treatment or dilute sulfuric acid (15-20%) medium temperature treatment.