Second, anti-rust treatment technology (a) anti-rust oil anti-rust treatment technology If the metal surface and cause atmospheric corrosion of various factors (ie, the metal surface protection), you can achieve the purpose of preventing the metal atmosphere corrosion, anti-rust Oil packaging technology is based on this principle to prevent corrosion.
Anti-rust oil is a temporary anti-rust paint consisting of oil-soluble corrosion inhibitor and other additive components. Anti-rust oil in the oil or resin material as a film-forming material applied to the metal surface, the corrosion factor has a certain degree of isolation. However, in general, oils and fats can dissolve a small amount of oxygen in the air, and can also dissolve a small amount of water. Simply using grease can not obtain a satisfactory anti-rust effect, so it is necessary to add corrosion inhibitors, which have very good anti-rust oil anti-rust effect. Great influence.
1. Principle of anti-rust oil action (1) Adsorption on metal surfaces Due to surface active substances, they share common features in molecular structure - two components that have hydrophilic polar groups and lipophilic non-polar groups. When the anti-rust oil is coated on the metal surface, the dispersed corrosion inhibitor molecules in the oil will be oriented and adsorbed on the interface between the metal and the oil (polar base and metal adsorption, non-polar base and oil adsorption), and can A multi-layered interface film is formed. Tests have shown that if only one or two molecular layers can be formed, the rust resistance is poor. When the adsorption layer is more than six molecules, it has good corrosion resistance. The adsorption form of the molecule is shown in Figure 6-10.
This kind of adsorption has a shielding effect on the corrosion factor. The second is to improve the adhesion of the oil film to the metal surface. Because the surface of the adsorption membrane is hydrophobic, it has better water resistance and at the same time can increase the resistance of the metal surface.
Many studies have shown that the chemical adsorption of corrosion inhibitors on metal surfaces (formation of coordination bonds) reduces the activity of metals, which is one of the main reasons for rust prevention.
(2) The interfacial tension between the water droplets and the oil layer falling on the oil film can be reduced.
If water droplets are formed on the surface of the oil film (such as condensation, etc.), the interfacial tension between the water droplets and the oil makes the water droplets spherical, so that it can easily penetrate into the oil film and reach the metal surface by gravity. Corrosion inhibitors such surface active substances can reduce the surface tension of water, so that the water droplets can not exist in the form of a spherical oil film, and tend to spread out. This reduces the pressure of the water droplet on the oil film, making it difficult to penetrate the oil film to the surface of the metal. The flatter the water droplets are spread on the surface of the oil film, the better the oil's anti-rust effect is. Therefore, measuring the contact angle of the water droplets on the oil film is the most commonly used method to identify the anti-rust effect of anti-rust oil (see Figure 6-11).
The relationship between the contact angle of water droplets on the oil surface and the interfacial tension is as follows:
So-Suo=Sucosθ
Cosθ=(So-Suo)/Su
Where: So - the surface tension of the oil Su - the surface tension of water Suo - the interfacial tension of oil, water (3) The displacement of water has a surface active corrosion inhibitor, can use its interface adsorption can be metal The surface adsorbed water is replaced. In addition, the water contained in the oil can be stabilized in the oil by the colloidal particles or the interfacial film of the corrosion inhibitor, so that it cannot be in direct contact with the metal.
The above-mentioned effects all have an inhibitory effect on the formation of a rusted battery on the metal surface, thereby achieving the purpose of preventing corrosion of the metal product.
2. Types of anti-rust oil There are many types of anti-rust oil. The anti-rust oils used for packaging metal products mainly include anti-rust grease, solvent-reduced anti-rust oil, thin-layer oil, and instrument anti-rust oil.
(1) Antirust Grease Antirust grease is a type of rust preventive oil based on petrolatum that is fat at room temperature. It consists of a film-forming substance (or base oil) and a corrosion inhibitor.
Film-forming substances (or base oils): Vaseline and lubricating oils are the main products. Vaseline is generally used in industrial petrolatum. Its chemical composition is paraffin 15%, petroleum jelly 45%, cylinder oil 25%, and mechanical oil 15%. Vaseline for rust preventive oils requires no tarnish, no moisture, and a certain degree of water resistance, dropping point temperature is 45 °C. Anti-rust oil commonly used lubricants are mechanical oil, spindle oil and cylinder oil. Its chemical composition is mainly alkane, naphthenic and aromatic hydrocarbons, as well as a small amount of oxides and sulfides.
Corrosion Inhibitors: Oil-soluble corrosion inhibitors commonly used in anti-rust greases include petroleum sulfonates, aluminum stearate, zinc naphthenate, oxidized petroleum grease, lanolin and its derivatives, etc. Added benzotriazole and so on. The type of corrosion inhibitor used in anti-rust grease can affect the performance of anti-rust grease. For example, anti-rust grease added with aluminum stearate has good salt water resistance, but its ability to adhere to metal is weak; anti-rust grease with antimony oil sulphonic acid added is more resistant to salt water and can be used for rust prevention in the marine atmosphere; The anti-rust grease with lanolin and its soap added has strong adhesion to metal, and it has a certain emulsifying ability for water, and strong rust resistance; zinc naphthenate anti-rust grease has strong adhesion to metal and has certain Salt water resistance, but poor rust resistance to cast iron; anti-rust grease with oxidized petroleum jelly and its soaps is superior to fatty acid soaps, but its salt water resistance is poor; anti-salt-80- synthetic lipids The rust grease has poor thermal stability and is rusting to copper. Benzotriazole, on the other hand, has excellent anti-rust effects on copper and its alloys. In order to obtain satisfactory results in practice, several corrosion inhibitors are often used in combination.
Anti-rust grease is in an ointment at room temperature, so the film is generally thick (up to 0.5mm), not easy to lose, not volatile, after sealing the package, the general rust-proof period is longer, up to two years or more.
The method of applying the rust-preventing grease is mainly a hot-dip method, that is, the rust-preventing grease is heated and melted to a flowing state before coating, and the washed, rust-removed, and dried metal product is immersed for a while, and then taken out and cooled to solidify the oil film. When hot-dip coating, the thickness of the oil film formed on the metal surface is different depending on the dip coating temperature of the same kind of oil. The lower the temperature, the greater the thickness of the oil film and the stronger its oil resistance. Large-scale parts can be hot brushed, that is, heating and melting rust-proof grease applied to the surface of metal products with a soft brush. After the metal products are oiled, they should be sealed with paraffin paper or plastic bags in time to prevent the oil layer from drying out. And pollution packaging.
(2) Solvent-diluted rust-inhibiting oils Solvent-diluted rust-inhibiting oils are composed of a rust-inhibitive oil that uses mineral oil or resin as a film former, and other additives such as antioxidants and stabilizers. Wait. This type of anti-rust oil can be divided into three types according to the types of solvents: petroleum series solvents, organic solvents, and water dilution. Among them, organic solvents are toxic and therefore have less application. According to the nature of the oil film, such anti-rust oil can be divided into hard film oil and soft film oil.
Hard film oils - Resins used as hard film oils should first have greater solubility in gasoline and kerosene, followed by rusting of various metals. The currently used resins include t-butyl phenol formaldehyde resin (ie 2402), long oil alkyd resin, melamine formaldehyde resin, terpene resin, petroleum resin and alkyl acid resin. Of these, 2402 resins and alkyl acid resins are preferred. Hard oils commonly used are hard-1, hard-3,1,2,74A-2. Hard -1 and -3 are 2402 resin film material, but hard 1 in a large amount of 2402, so the oil film toughness is not suitable for edge sharp metal products, and may be powdered in long-term sealed packaging , And hard-3 in 2402 content is less, and added 389-9 alkyd resin to improve the toughness of the oil film. However, hard-3 is less adaptable to non-ferrous metals such as copper alloy than hard-1. For ease of identification, there is a small amount of 3902 oil-soluble red pigments in the hard-3. 74A-2 is a hard alkyd oil based on alkyl acid amino resin and oxidized petroleum film soap. It is suitable for a variety of metals (including magnesium alloys) with good stability and strong adhesion. Hard film anti-rust oil has good film-forming protection, smooth and non-sticky film surface, no winter does not crack in winter, and convenient construction, cheap, but its hard film is not easy to remove. The natural drying time of film formation is about 1 h.
Soft film oil - commonly used soft film oil has 204-1, Shanghai stone -201, F-35,112-5,704,3 anti-rust oil, 33-612 and soft -1 and so on. 204-1 oil is a sulphonated lanolin calcium soap as a film former and is also a corrosion inhibitor. Shanghai Shi-201 and F-35 are Vaseline as a film former. 112-5, 704, 3 anti-corrosion oil, 33-6, and soft-1 are all anti-corrosion oils that use oxidized petroleum jelly soap (T743 soap) as a film former and corrosion inhibitor. The main characteristic of solvent-based soft film oil is that the metal surface can form a film, so the loss is small but it is not easy to remove. The rust-proof period is short.
As rust-proof oil has many deficiencies as a rust-proof seal coating, such as environmental pollution during construction, affecting the appearance of metal products, and in addition to the use of membrane. Therefore, the anti-rust coating for storage has gradually been replaced by thin films and ultra-thin films.
The film anti-rust coating can form a complete film with a thickness of 1 to 2 μm. The film has strong adhesion to the metal surface. The film has good rust resistance and does not affect the performance of the lubricant. When used, no rust removal is required. Currently, thin-film and ultra-thin-film anti-rust paints mainly include polyvinyl fluoride and polyvinyl fluoride types, and other synthetic resin types, organosilicone ammonia, and silicone resin types.
Solvent dilution type anti-rust oil in the soft film oil, mainly for the storage of metal products, can be sprayed or dip coating method (the amount of solvent can be less); then sealed with a plastic bag. The main coating method of hard coating oil is sprayed with compressed air, but this spray coating method will not be able to be sprayed locally. The metal surface with no anti-rust coating will continue to rust in the air, and even rust will be faster.
(3) Thin layer oil This is a rust-preventing oil that is a film-forming material such as a resin. It is characterized by a long rust-proof period, a thin and transparent oil film, and a good appearance and consumption. Thin oils are solvent-based and solvent-free.
Thin oils are usually dip or sprayed.
(4) Instrument anti-rust oil This is a kind of low-viscosity anti-rust oil, which is mainly based on the addition of corrosion inhibitors such as lubricating oils and other liquid mineral oils. It is commonly used for the complete immersion storage and packaging of instruments and instrument parts. That is, in a sealed container, anti-rust oil is added, the meter or precision parts are completely immersed in oil for sealing, or dip-coating and sealed packaging are used.
(2) Vapour-phase anti-rust packaging technology VCI anti-rust packaging technology is a vapor phase corrosion inhibitor (volatile corrosion inhibitor), in the sealed packaging container for metal products rust prevention technology. A vapor phase corrosion inhibitor is a substance that slows down or completely stops the metal's destruction process in aggressive media. It is volatile at room temperature and it volatilizes or sublimates in a short time in a sealed packaging container. The corrosion gas can fill the corners and crevices in the entire packaging container and adsorb on the surface of the metal products at the same time, thus suppressing the effect of atmospheric corrosion on the metal. Since the vapor phase rust-proof packaging technology does not need to be coated on the surface of metal products, this rust-proof packaging method does not affect the appearance of the metal products. When the products are used, the peeling process of the products is also omitted, and at the same time it does not contaminate the packaging. The rust-proof period is long, effective rust-proof period can reach 3 to 5 years, and some can reach 10 years or more. However, its ability to inhibit sweat rust is poor, and many vapor phase corrosion inhibitors cannot be used in a variety of metal assemblies and have a pungent odor.
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