When disassembling and repairing diesel generator sets, it is sometimes found that some equipment is rusty. So how to deal with rusty diesel generator equipment? Metal rust occurs when the metal surface comes into contact with oxygen, moisture, and acids in the air to form oxides. The main methods of rust removal include mechanical method, chemical pickling method and electrochemical acid etching method.
(1) Mechanical method
The mechanical method uses friction, cutting and other effects between mechanical parts to remove the rust layer on the surface of the parts. Commonly used methods include brushing, grinding, polishing and sandblasting. Single piece and small batch repairs rely on manual brushing, scraping or polishing of the rust layer with wire brushes, scrapers, emery cloths, etc. Batches of parts or qualified units can use electric motors or pneumatic machines as power to drive various rust removal tools for rust removal, such as electric grinding, polishing, rolling, etc. Sandblasting rust removal uses compressed air to spray sand of a certain particle size on the rusted surface of the parts through a spray gun. It not only removes rust quickly, but also prepares it for painting, spraying, electroplating and other processes. The surface after sandblasting is clean and has a certain roughness, which can improve the bonding force between the covering layer and the parts. Mechanical rust removal can only be used on the surface of unimportant mechanical parts.
(2) Chemical method
Chemical method, this is a pickling method that uses chemical reactions to dissolve the rust products on the metal surface. The principle is that the acid dissolves the metal and the hydrogen generated in the chemical reaction acts mechanically on the rust layer to cause the rust layer to fall off. Commonly used acids include hydrochloric acid, sulfuric acid, phosphoric acid, etc. Depending on the material of the metal, the chemicals used to dissolve the rust products will also vary. The selection of rust removal chemicals and their operating conditions are mainly determined based on factors such as the type of metal, chemical composition, surface condition, part dimensional accuracy and surface quality.
(3) Electrochemical acid etching method
The electrochemical acid etching method is to place parts in an electrolyte and apply direct current to achieve rust removal through chemical reactions. This method is faster than chemical methods, better preserves the matrix metal, and consumes less acid. Generally divided into two categories: one uses the parts to be rusted as the anode; the other uses the parts to be rusted as the cathode. Anode rust removal is due to the dissolution of metal after electricity is applied and the tearing effect of oxygen in the anode on the rust layer, causing the rust layer to separate. Cathodic rust removal is due to the hydrogen generated on the cathode after electricity is applied to reduce the iron oxide and the hydrogen tears the rust layer, causing the rust to fall off the surface of the part. The main disadvantage of the above two types of methods is that when the current density is too high, it is easy to corrode excessively and damage the surface of the parts, so it is suitable for parts with simple shapes. Although the latter has no over-corrosion problem, hydrogen easily enters the metal, causing hydrogen embrittlement and reducing the plasticity of the parts. Therefore, the appropriate rust removal method needs to be determined based on the specific conditions of the rusted parts.
In addition, in production practice, rust removal liquids prepared from a variety of materials can be used to combine oil removal, rust removal and passivation into one treatment. In addition to zinc, magnesium and other metals, most metals can be used regardless of size, and spraying, brushing, dipping and other methods can be used.
