Let’s talk about the protection of metal materials

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The main methods for preventing metal corrosion must be considered from both the metal and the medium perspectives. Material protection can be considered from the following aspects, which can help us address the issue of metal corrosion. 1. Select materials appropriately and pay attention to the processing techniques. Protecting materials is a comprehensive task that constitutes an important part of production, requiring coordination from various aspects and seamless integration across different stages. When selecting equipment and engineering materials, it is necessary to use materials with good stability under the given corrosion conditions, as much as possible, while meeting the main technical, process, and economic requirements for production. For example: metal lining of lead and ceramic materials are used in the H2SO4 solution storage tank ； When constructing outdoor structures, metal aluminum and its alloys should be used whenever strength permits, as aluminum does not corrode easily in normal air due to an oxide film layer that protects its surface. In terms of design, the structure and combination of equipment and systems should comply with corrosion prevention principles. Try to avoid the overlapping and riveting of different metals. There should not be too many welds, and the stress on each part must be even. In terms of technical specifications and production processes, if there is a choice, factors such as low reaction temperature, low pressure, minimal generation of corrosive by-products, less stringent corrosion prevention requirements, and easy equipment maintenance should be given priority. 2. Coating protection: Methods that involve using corrosion-resistant materials to cover the substrate to be protected, thereby preventing it from coming into direct contact with corrosive agents and avoiding corrosion, all fall under this category. The most common and simplest method is to coat the metal surface with non-metallic materials such as anti-corrosion coatings, plastics, rubber, enamel, ceramics, glass, and stone. Furthermore, a layer of metal or metal alloy with good corrosion resistance, such as Ni, Cr, Zn, Al, Sn, Cu, etc., can be deposited on the metal surface through chemical plating, electroplating, thermal spraying, or hot-dip coating. Metal coating protection can be divided into cathodic coating protection and anodic coating protection. The metal used as the coating layer on the anode should have a more negative electrode potential than the base metal; for example, Zn, Al, etc. can be used as coatings on iron ； The electrode potential of the metal in the cathodic coating is more positive than that of the base metal being protected. For example, when Ni, Cu, Sn, Pb, etc., are coated on iron, the base metal acts as the anode while the coating functions as the cathode; therefore, the coating must be intact in order to achieve protection of the substrate. 3. Electrochemical protection: The necessary conditions for electrochemical corrosion are an anode, a cathode, a dielectric, and an electrical current path. Removing or altering any one of these conditions can prevent or slow down the progression of corrosion. The coating isolates the dielectric surrounding the metal, and it also serves an electrochemical anti-corrosion function. Electrochemical corrosion protection is mainly achieved through cathodic protection and anodic protection. 4. Treatment of corrosive media: Depending on the composition and properties of the corrosive media, appropriate treatment is carried out; generally, substances that are corrosive or contribute to corrosion are removed from these media, and corrosion inhibitors are added to them as well.