Discussion on the causes of yellowing of steel plate phosphating Zhengxiong Machinery Co., Ltd. Zhengzhou 450001 Wang Gefa yellowing Document identification code B Article number 1001 Phosphating of chemical conversion film steel plate, especially in the presence of oxidizing accelerator When zinc-based phosphating in the presence of various additives such as film-forming additives. The chemical process is very complicated. The reactions involved include ionization. hydrolysis. Displacement neutralization. precipitation. Complex. Redox, etc. There are more than ten reactions catalyzed by nitrate or nitrite alone, and the complexity of other related reactions is remarkable. The complexity of chemical reactions also lies in the fact that some reactions are merely reasoning. Despite this, the research on phosphating reaction is still gradually deepening, 1 acceleration of phosphating 1.1 acceleration of phosphating reaction ⑴ heating phosphating reaction is an endothermic process. Heating facilitates the introduction of electropositive metals into the reaction. For example, a small amount of copper salt is added to the phosphating solution. A replacement reaction occurred. Generated, 1 is deposited on steel. There are many micro-cathode on steel. The steel reacts electrochemically, the corrosion is intensified, and the rate of phosphating film formation is accelerated. Depolarizer, its role is to expose the crystal nucleus without being covered by hydrogen. When there is an oxidizing accelerator. The hydrogen atoms are directly oxidized into water. Does not affect the diffusion of ions. Forming, chemical film. 1.2 Acceleration of phosphating film deposition process The method of achieving acceleration is generally to introduce crystalline nuclei. The titanium salt surface before phosphating is adjusted to form a nucleus active center on the workpiece surface, so that phosphating crystals can be generated along the nucleus when there is no crystal, although it is difficult to form the product. Excessive 21 gills. , 0 Guang Cun surpasses supersaturation; Rong Lang; 2 Phosphating yellowing phenomenon and cause analysis 2.1 Yellowing at low catalytic concentration as the metal corrosion reaction progresses. The precipitates accumulate in the microcathode area, forming Qiu, which is oxidized to water. Go from Yin Anluo. It is the polarization of the above reaction on the cathode that accelerates the departure of Dinby and the elimination of 1, when the catalyst concentration is low. Zhang Du slow. 21 It is difficult to hydrolyze a sufficient concentration to form a complete phosphating film; when the catalyst concentration is low. The cathode is harder to leave. Without sufficient arsine active centers, a complete phosphating film cannot be formed. Due to the metal, 6 is exposed to the air. Oxidation to 623, yellowing phenomenon, 2.2 yellowing when the total acidity is high, the phosphating solution as a buffer solution system. The total acid of the phosphating solution is provided by +, H2POtHPd. Production control of free acid. Controlled; the total acid concentration of plant 1 is too high, and it is too high, 1104. The high concentration of the buffer solution has a high buffer strength, which causes the acidity in the limited diffusion layer on the workpiece surface to be difficult to reduce. 0 concentration is too low to form a phosphating film. The same phosphating solution for the tank and replenisher. The accumulation of total acid is a frequent phenomenon. In order to control the quality of the phosphating solution, in addition to the determination of free acid, the total acid or the total ratio of acid to free acid is also; 1; call it detection. When preparing. Adjust the dosage of 1 salt to reduce accumulation. During production, it is true that yellowing is caused by high total acid. It can be added 2.3. Yellowing free acid when the free acid is high is an important parameter of the phosphating solution. In the phosphating solution, when the free acid is high, the value is 04.6. 4.2 is the main component. Special money. Surface phosphide film 304 exposed metal is oxidized to form a yellow oxide. 2.4 Yellowing at the time of failure of surface adjustment After the degreasing of the steel plate without surface adjustment, yellowing after phosphating, this problem can be explained by the lack of active centers. The crystal grains of the phosphating film form more cathode lattice reaction points on the cathode lattice on the workpiece surface. The crystal structure of the phosphating film becomes finer, denser and firmer; vice versa. Phosphating particles are coarse and sparse. After alkaline degreasing, many lattice points on the steel surface will be neutralized. That is, in the production of phosphating, the degreaser is sometimes mistakenly added to the adjustment tank, which causes yellowing of the phosphating film, indicating that there are few active centers, and the phosphating film layer cannot be closely connected to block the steel substrate and the oxygen phosphating liquid to the adjusting tank. The channeling also leads to the failure of tuning. There is a large amount of green precipitated nickel at the bottom of the tank. Spray phosphating, when the local nozzle is not open, the part will be yellowed. Adjustment of titanium salt Adding copper salt and nickel salt to the phosphating solution can make the phosphating film fine. Many phosphating crystal nuclei are observed by scanning electron microscope. There are hundreds of thousands to nearly one million grains on the 2 side. These grains are formed within a few seconds after the reaction starts. These grains only increase but not increase. Therefore, the purpose of various pretreatments before phosphating is how to expose the active grains. And try to protect or increase the number of grains. 2.5 A good phosphating solution formulation with short phosphating time and yellowing requires a certain phosphating time. Preparation and application of manual control multifunctional metal cleaning agent Department of Chemical Engineering, Jiaozuo University 454151 Liu Changchun Shi Xiangyu Keywords 1 metal cleaning agent surfactant water tolerance 1 classification number 1T; i74. Although metal cleaners have developed rapidly in recent years, there are many varieties. However, the solid cleaning agents currently on the market have large alkalinity and poor solubility, and the cleaning speed is slow. Generally, it is necessary to wash and wash the steel parts after heating and washing. The surface of the steel is easily rusted, and the water-based metal cleaning agent also has some problems in the rust prevention cost after washing at room temperature. Can not replace oil or organic solvent cleaning agent. Its application is subject to many restrictions. In this paper, a multifunctional oil-based metal cleaning agent was developed. It is made up of fast penetrant surfactant surfactant cosolvent antirust agent enhancer and bactericide. 1 The experiment will pull apart the powder, ethanolamine. Swire oil, cellosolve, penetrating agent evaluation 0. Sodium nitrite, builder thickener 6501. Sodium polyphosphate, isopropyl alcohol, formaldehyde and water are mixed into a multifunctional metal cleaning agent in proportion. Dissolve the sodium nitrite, dissolve the powder, and dissolve the sodium polyphosphate with water; finally add the cellosolve and methazide to stand and filter it to be the finished product. Non-ionic surfactants Zuan 0 and 650, among which the pull-out powder and Zuan 0 are fast penetrants, have strong penetrating and emulsifying ability for oil stains. Both Taikoo Oil and 6501 have good washing ability. Also has anti-rust properties. The low molecular weight co-solvent is soluble in both water and organic solvents, greatly reducing the macular surface of the solvent washing machine surface. Wipe it. It is also excellent in degreasing treatment before paint phosphating electroplating, and its technical performance index. Test results Test results Appearance Self-test uniformity No layering No precipitation Water and volatile value 3 aqueous solution, 250 net washing power 3 aqueous solution, 60, 45 steel and 23, cast iron, grade 0 corrosion amount 45 steel and 23, cast iron, grade 0 Rinsing performance The stainless steel sheet has no cleanable detergent residues and is not uniformly layered. The low-temperature stability is 5 ± 2. The uniformity is not layered and there is no crystallization or precipitation. The comprehensive anti-rust ability of the anti-rust sodium nitrite ethanolamine is extremely strong. The anti-pounding period of common carbon steel after cleaning is more than 3 months. The anti-pounding performance can be adjusted according to its use. 3 Application of multifunctional oil-based metal cleaning agent is suitable for paint electroplating and phosphating. Pre-degreasing treatment of surface oxidation and other metal processing and various vehicle machine tool bearings. The main feature of the degreasing cleaning of plastic products and chemical equipment is the rapid decontamination at room temperature, and the advantages of both water-based cleaning agents and oil-based cleaning agents. The product is suitable for dipping and spraying. people. Ultrasonic and other cleaning methods. Non-toxic and non-flammable when used. The emissions are less polluting than those from oil cleaning. The amount of oil pollution per ton of cleaning is more than 3 times that of gasoline. Not only can energy be saved, but cleaning costs can also be significantly reduced. Responsible editor Zhang Fan for spraying, chemical, when, chemical segment consists of two sets of chestnuts and nozzles. The failure of the group pump can lead to short phosphating time; when the phosphating section is supplied with phosphating liquid by the group pump. Nozzle and pipeline failure may make the phosphating solution contacted by the steel plate intermittently. The phosphating time is now short. Especially in the zinc phosphating system with a large amount of sediment. This form of influence is typical; when using a conveyor chain, the speed of the chain is too fast is also an influencing factor. Found in production. When the production line is shut down, 5+ stops. In terms of staying in the phosphating section, short time is an important cause of yellowing defects. The arsonization time is short. Although the number of crystal nuclei is sufficient. However, the 23 and 42 crystal nuclei were too late to grow up and were independent. It does not form a dense protective film that effectively shields oxidizing media. Causes oxidation of the base metal and yellowing. 3 Conclusion, chemical reaction is the process of crystal formation. First of all, the dissolution of the metal is needed to reduce the acid team that is recognized, and 1 is sufficient. Necessary conditions for the full ion product concentration such as the cadaver solubility product constant such as Yushu; secondly, sufficient crystal nuclei are needed to provide the basis for the growth of the crystal; and finally. It takes enough time for the crystal to grow. The crystals are closely connected to each other. Start with the above points. Accelerating phosphating and solving the quality defects of phosphating can often achieve the desired results. Responsible Editor Zhang Fan
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