Metal corrosion and its prevention methods

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Rusting of metals and its prevention methods 1. The main factors affecting metal rusting can be summarized as follows: (1) The chemical composition and structure of the metal material itself； (2) Metal surface finish (oxygen concentration difference cell corrosion) ； (3) Components of the solution in contact with the metal surface and pH value ； (4) Ambient temperature and humidity ； (5) Various environmental media in contact with the metal surface. 2. Surface pretreatment methods for the objects to be protected from rust: (1) Surface cleaning. The cleaning method must be selected appropriately based on the properties of the surface to be rust-proofed and the prevailing conditions. Commonly used methods include solvent cleaning, chemical treatment cleaning, and mechanical cleaning. (2) After cleaning the surface, it can be dried by blowing with filtered dry compressed air, or using a dryer at 120–170°C; it can also be dried with clean gauze. ⑶Method of applying rust preventive oil: ① Immersion method. Some small items are immersed in rust-preventing grease, allowing a layer of it to adhere to their surfaces. The oil film thickness can be achieved by controlling the temperature or viscosity of the anti-rust grease. ②Brush application method. For outdoor building equipment or products with special shapes for which dipping or spraying is not applicable, when applying the coating it is necessary to be careful to avoid accumulation as well as to prevent missed areas. ③Spray method. Some large anti-rust coatings cannot be applied using the immersion method; instead, filtered compressed air at a pressure of about 0.7 MPa is used for spraying in a clean environment. This method is applicable to solvent-diluted rust preventive oils or thin-layer rust preventive oils, and proper fire prevention and personal protective measures must be taken.