Degreasing cleaning on the surface of steel drum Text / Xin Qiaojuan There are many factors affecting the quality of steel drums, and the surface treatment process of steel drums is an important part of them. Specifically, there are many details to be noted in the degreasing cleaning, phosphating treatment, and rust removal treatment of the surface of the steel drum. Neglecting a certain detail may leave defects that should be avoided, which may affect the quality of the steel drum. The degreasing cleaning of the surface of the steel drum is also called degreasing cleaning. Degreasing cleaning usually uses an alkaline solution, an organic solution as a cleaning agent, and a cleaning method such as dipping, spraying, or the like. First, alkaline elution grease The lye degreasing cleaning is mainly based on the functions of emulsification, dispersion, dissolution and mechanical action. The oil stain on the surface of the steel drum is generally mineral oil, which is a non-saponified neutral oil. It cannot react with the alkali. In the cleaning process, the strong alkali is used to cause the oil to dissociate from the surface of the steel drum. Common lye cleaning agents for steel drum cleaning include: 1. Sodium hydroxide, also known as caustic soda, is a strong alkaline compound. When cleaning, it mainly acts to dissociate oil. It does not have the buffering effect of alkaline salt. It has no erosion effect on steel drum at normal temperature and medium temperature; it can produce slow corrosion in high temperature. Sodium hydroxide is cheap, but it has a strong corrosive effect on human skin; therefore, care should be taken when handling it. 2, sodium carbonate, also known as soda ash, is a low-cost alkaline salt. It has a buffering effect and does not erode steel drums like strong alkali. Sodium bicarbonate (also known as soda) and trisodium hydrogencarbonate are weaker in basicity, but they can react with calcium ions in water to form soluble salts, which have certain properties for hard water. Softening effect. 3. Silicate, including sodium metasilicate, sodium orthosilicate and water glass. The silicic acid formed during the hydrolysis of the silicate is insoluble in water, and is suspended in the bath in a colloidal state to disperse the solid dirt. The alkalinity of sodium orthosilicate is close to caustic soda. Because of the strong colloidality of the silicic acid contained in it, it has the advantage of dispersing and retaining the dirt, so it is often used in the cleaning of steel drums with caustic soda. The general characteristic of silicate is that the lye is excellent in moisture and permeability, and maintains the dispersibility of the soil and the hard water resistance, and has a certain anti-corrosion effect on the surface of the steel drum. 4. Phosphate, as an alkaline cleaning agent, includes trisodium phosphate, tetrasodium pyrophosphate and sodium tripolyphosphate. Phosphate has a more pronounced dispersion which disperses large particulate soils into small particles resembling colloidal particles. Tetrasodium pyrophosphate also has a surface active effect. Phosphate can also be used as a multivalent integrator. It combines with calcium and magnesium ions in hard water to form a water-insoluble salt. The common characteristic of phosphate is to inhibit the corrosion of the metal surface of steel drums. However, due to its low alkalinity and high price in alkalis, it is rarely used as a cleaning agent by steel drum manufacturers, but often with low price. The combination of strong and reduced. The alkaline washing process commonly used in steel drums is immersion cleaning and spray cleaning. Immersion cleaning is to soak the steel drum in the cleaning tank, so that the whole surface is in contact with the alkali liquid. In order to ensure the degreasing effect, the cleaning time can be heated and extended, and the flow speed of the alkali liquid can also be accelerated, such as stirring with a mixer, circulating pump circulation, etc. . The spray cleaning uses a spray cleaning device to spray the alkaline cleaning liquid onto the surface of the steel drum for cleaning. The spray cleaning has the functions of saponification, emulsification, etc. of the detergent, and also has the effect of jet impact. The greater the injection pressure, the greater the proportion of mechanical detergency in degreasing. The composition of lye is the main factor affecting the quality of steel drum degreasing. Alkali degreasing relies on saponification, wetting, emulsifying, dispersing, etc. to remove oil stains. Because a single material does not have these properties at the same time, a combination of materials is required. The formula is appropriate for the best overall performance. The high concentration of the alkali solution is favorable for the saponification reaction, and the higher the concentration of the alkali liquid, the lower the surface tension between the oil stain and the solution, and the oil stain is easily emulsified. Practice has shown that when the pH of the solution is below 8.3, the solution hardly degreases. Practice has proved that in the degreasing process of the steel drum, the high temperature of the lye is beneficial to the saponification reaction, and the oil with higher melting point is softened, which is beneficial to the infiltration and emulsification, so the cleaning effect of the high temperature steel drum is good. . In general, the temperature of the solution should be between 70 and 100 °C. The mechanical action contributes to the removal of oil stain on the surface of the steel drum, and the mechanical action is strong, and the cleaning effect is good. Stir the solution properly during immersion cleaning. Spray cleaning should maintain a certain flushing force on the steel drum, usually between 50KPa and 400KPa. The addition of a suitable surfactant to the alkali cleaning solution can reduce the interfacial tension, improve the wettability and emulsifying properties, and improve the cleaning effect. However, surfactants are prone to foaming. When using immersion cleaning, more cationic and nonionic surfactants can be added without affecting the cleaning operation due to foaming. However, when spray cleaning is used, even if a small amount of surfactant is used, it is easy to cause a large amount of foam to accumulate outside the tank, which not only contaminates the work site, but also causes the loss of the cleaning solution, so that the production cannot be continuously performed. To overcome the large amount of foam generated during spray cleaning, a low foaming surfactant can be used and the amount used can be controlled or an antifoaming agent can be added. Silicone oils, higher alcohols, poorly water-soluble benzoic acids and volatile petroleum solvents all have defoaming action. After the steel drum is degreased and washed in the alkali solution, the water is rinsed to remove the cleaning agent remaining on the surface of the steel drum. Because the residual cleaning agent will affect the adhesion of the coating, and the alkali and salt in the cleaning agent absorb moisture, it will cause early foaming of the coating. The water washing can be carried out by dipping or spraying. Steel drums are often washed with two stages of water, one with hot water and the other with cold water. The temperature of the hot water should not be too high, generally controlled at around 60 °C. When using the second-stage water washing, which level of hot water is more suitable should be determined according to the specific conditions of the steel drum cleaning. If the cleaning agent used is not easily washed away with cold water, the first stage water washing should be hot water. If the cleaning agent used is easy to wash off with cold water or if there are many cleaning agents attached to the surface of the steel drum, it needs to be washed with running water. The first stage water washing should use cold water to avoid a large amount of heat. If multi-stage reverse cleaning is used, the quality of washing can be improved, water consumption can be saved and wastewater discharge can be reduced. After the steel drum is rinsed with water, it should directly enter the rust and phosphating process and then dry. If you do not directly enter the descaling and phosphating process, you should also dry it first. Compressed air can be used to blow off water or water from the surface of the steel drum before drying. Generally, it can be dried at 100 ° C for 1 min to lOmin. If there is yellow rust in the drying process, a small amount of anti-rust corrosion inhibitor, such as triethanolamine, can be added to the water in the last washing to adjust the pH of the water to 8-9, which can effectively prevent the generation of yellow rust. Second, solvent degreasing The degreasing ability of various oils by means of organic solvents is widely used in the barrel industry. Organic fluxes have high degreasing efficiency, but they cannot wash off inorganic salts and bases. In the coating process, the organic solvent commonly used for oil removal is white alcohol (also known as paint gasoline, boiling point of 100-200 ° C, flash point of 30 ° C) or cleaning gasoline (boiling point of 80-120 ° C) and various An oxygen solvent such as trichloroethylene. However, due to the high toxicity of chlorine-containing solvents, most barrel companies use gasoline scrubbing. Because hydrocarbon solvents such as gasoline used for solvent cleaning are flammable and explosive, and halogenated hydrocarbon solvents are limited by toxic or ozone depleting, safe, non-toxic, mild surfactants or mixed solvents are degreased in steel drums. The new direction. The surfactant aqueous solution and the mixed solvent are used as a steel drum cleaning agent, and the surface oil is cleaned by the characteristics of low surface tension, good wettability, and strong emulsifying power. With the development of various new synthetic surfactants, especially after the development of non-foaming or less foaming cleaning and biodegradable surfactants, surfactants have been widely used in the cleaning of steel drums. The aqueous solution of the surfactant and the mixed solvent have the advantages of better cleaning ability under the same conditions than the alkali liquid, good oil removal effect, weak alkalinity, little erosion to the steel drum, and can be combined with other steel drum surface treatment processes. For example, the process of de-oil cleaning and phosphating two-in-one treatment can achieve the purpose of simplifying the process under certain conditions. After the biodegradable surfactant is used, it is advantageous for the sewage treatment of the surface treatment process. The degreasing mechanism of a surfactant generally consists of three stages. The first stage wets the surface of the steel drum and causes the oil to roll off. Due to the adhesion of oil stains and the adsorption of trace amounts of air, the surface of the steel drum has a large interfacial tension and is not easily wetted by water. When the surfactant is added to the water, the surfactant is easily adsorbed at the steel drum-water interface and the oil-water interface, reducing the interfacial tension, replacing the gas on the surface of the steel drum, infiltrating into the surface of the steel drum and between the oil and the oil. Between the oil stain point, the surface of the steel drum is preferentially wetted, and the oil film is curled into oil beads to leave the surface of the steel drum. The second stage transfers the oil off the solution to the solution. The emulsion with emulsification acts at the oil-water interface to form an emulsion with certain stability, or dissolves the water-insoluble oil into the surfactant micelle by the solubilization of the surfactant. in. Both of these methods allow the oil to be removed to be transferred to the solution. The third stage traps the oil entering the solution in the solution. Since the adsorption film surrounding the oil stain point has sufficient mechanical strength to be broken by the collision, the oil stain will not accumulate again, and the dispersed oil stain point is trapped in the solution and will not be deposited on the surface of the steel drum to cause secondary pollution. The surfactant-cleaning agent for removing oil is composed of a surfactant, a cleaning aid, and an additive. The surfactant is generally prepared by combining an anionic surfactant having strong detergency and a nonionic surfactant. The cleaning aid is generally an alkaline substance such as tripolyphosphoric acid, and the purpose is to make the cleaning liquid alkaline to improve the degreasing ability, the surfactant does not cause corrosion to the steel drum, but the ability to remove old viscous oil is poor. The mixed solvent used for the degreasing cleaning may be in various forms such as a lipophilic organic solvent and a surfactant mixture, a mixture of an organic solvent and an aqueous alkali solution. When the lipophilic organic solvent is present in an emulsified or solubilized state in an aqueous surfactant solution, the two synergistically act to make the cleaning ability better. The degreasing ability of the solvent formed by the alcohol or ether hydrophilic organic solvent and the aqueous alkali solution is higher than that of the solvent alone, and the flammability is greatly reduced. In addition, there is an emulsion cleaning agent which is a mixed solution in which an emulsifier disperses an organic solvent in water. The organic solvent in such an emulsified cleaning liquid is usually a petroleum fraction having a boiling point of from 60 ° C to 210 ° C. The emulsifier has an anionic surfactant and a nonionic surfactant. In order to make the emulsifier have a certain solubility in an organic solvent, some water-soluble coupling agents are often added. (China Packaging News) Kitchen Pull Out Wire Basket,Kitchen Cabinet Plastic Waste Bin,Kitchen Drawer Sliding Basket,Kitchen Wire Drawer Basket Foshan Gruwill Hardware Products Co., Ltd. , https://www.gwwirebasket.com