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Electroplating is a key surface treatment technology in the automotive industry, which not only enhances the corrosion resistance and aesthetics of metal parts, but also improves the quality and performance of the whole vehicle. However, pickling, an important step in the electroplating process, while essential to remove oxide layers and impurities from metal surfaces, also poses some technical challenges, especially in preventing hydrogen embrittlement. This article aims to ** the key considerations for pickling in electroplating and how to effectively take measures to prevent hydrogen embrittlement and ensure the strength and durability of metal parts.
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Introduction to the pickling process
Pickling is a critical pre-treatment step in the electroplating process and has a significant impact on the final plating result. The main purpose of pickling is to remove oxide layers, rust and other contaminants from metal surfaces, thereby providing a clean, activated surface for electroplating. This process is not only related to the adhesion of the coating, but also directly affects the appearance and performance of the coating.
The pickling process usually uses dilute sulphuric acid or hydrochloric acid as the main pickling agent. These acids are effective in removing oxide and rust from metal surfaces, but they can also have a corrosive effect on metal surfaces. Therefore, the acid concentration, temperature and treatment time need to be strictly controlled during the pickling process to ensure that the metal surface can be cleaned effectively without excessive damage to the material.
During the pickling process, special attention is also required to pay attention to the treated waste liquid. Pickling waste contains heavy metals and corrosive chemicals that must be properly treated and disposed of to prevent environmental pollution.
In order to ensure the effectiveness and safety of the pickling process, the managers and operators of the electroplating plant need to have an in-depth understanding of the pickling process and strictly follow the operating procedures. Below, we will detail the specific things that should be paid attention to when pickling in electroplating.
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Improvement of the pickling process and its precautions
In the electroplating process in the automotive industry, pickling is a critical step to remove rust from metal surfaces. Rust is mainly composed of oxides and hydroxides of iron. These are usually removed by the synergistic action of acid components (e.g. hydrochloric acid) and surfactants, a process that involves dissolution and exfoliation. However,Traditional pickling methods have some drawbacks, such as high acid concentrations that can lead to overcorrosion and environmental problems.
To this end, we have taken the following improvement measures:
1.Reduces acid concentration:Reducing the acid concentration, such as the hydrochloric acid from 30% to 35% by mass, can reduce acid consumption, improve the environment, and improve the surface quality of the workpiece. The low-concentration acid solution can quickly penetrate the interface between the oxide scale and the matrix under the action of the wetting agent, initiating a chemical reaction (Fe+2HCl=2FeCl2+H2), and at the same time, the mechanical exfoliation of hydrogen is used to clean the surface. The use of DS857 acid descaler can reduce the corrosion of bare substrates and reduce the useless consumption of acids.
2.Use of mixed acids:Mixing hydrochloric acid and sulfuric acid in the right proportions, combined with the properties of both acids, can increase the speed of rust removal and reduce the operating temperature.
3.Adopt multi-functional and efficient degreasing and rust remover:Such as multifunctional pickling of degreasing powder and activated salt, which marks the progress of the steel pickling process.
4.The use of a special pickling process:Different pickling processes are adopted for workpieces of different shapes and uses, and the pickling process is individualized.
Precautions during pickling:
When carrying out pickling, special attention needs to be paid to the following:
Workpiece pre-ProcessingBefore pickling, ensure that the surface of the workpiece is free of grease and other impurities to improve the pickling effect.
Control acid concentration and temperature:Proper acid concentration and temperature are essential to prevent overcorrosion and optimize rust removal efficiency.
Security Measures:Pickling is a chemical process with certain dangers. Appropriate safety measures, such as the use of protective gear, must be in place to ensure good ventilation.
Waste Disposal:The waste acid and sludge produced after pickling must be properly disposed of in accordance with environmental standards.
Through the implementation of these improvement measures and precautions, the pickling process can be more efficient and environmentally friendly, while ensuring product quality.
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Measures to prevent hydrogen embrittlement in pickling in electroplating
Pickling is a critical step in the electroplating process in the automotive industry, but it also introduces the risk of hydrogen embrittlement. Hydrogen embrittlement is a phenomenon caused by the penetration of hydrogen atoms into the metal, which is especially dangerous for high-strength steels.
Here are a few effective measures to prevent hydrogen embrittlement:
1.Use of multifunctional retardant inhibitors:These products not only have the effect of inhibiting corrosion, but also effectively inhibit the penetration of hydrogen. They speed up pickling, reduce hydrogen uptake, and increase corrosion inhibition.
2.Strict control of pickling conditions:The results show that the amount of hydrogen infiltration of steel in the pickling solution has little relationship with the acid concentration, but has a great relationship with the pickling temperature and time. It is advisable to use a high concentration of acids and to shorten the pickling time, especially for high-speed steel and other high-strength steel grades. Controlling the temperature and time of pickling can effectively reduce the permeation of hydrogen.
3.Prevent contamination of pickling liquids:When the pickling solution contains certain metal impurities (such as phosphorus, arsenic, tin, mercury, lead, zinc, cadmium, etc.), it increases the permeation of hydrogen, thus increasing the risk of hydrogen embrittlement. Therefore, it is necessary to keep the pickling solution pure and avoid contamination by these impurities.
4.Hydrogen flooding treatment:For pickled workpieces, a hydrogen displacement treatment of 180 200 °C is recommended for 3 4 hours. This treatment effectively removes the permeated hydrogen and reduces the risk of hydrogen embrittlement. If hydrogen permeation is found, hydrogen flooding should be carried out as soon as possible to avoid failure due to hydrogen embrittlement.
Overall, the importance of pickling as an indispensable step in the electroplating process in the automotive industry cannot be overstated. By implementing these improvements and protection strategies, we can not only effectively improve the quality and performance of metal parts, but also greatly reduce potential risks such as hydrogen embrittlement. These measures are not only about technological innovations, but also about environmental protection and operational safety, demonstrating that the automotive industry is fulfilling its social responsibilities while continuing to strive for technological excellence. With the continuous development and application of new technologies, we expect the electroplating industry to continue to develop in the direction of being more efficient, environmentally friendly and safe.