The quality of electroplated parts directly affects the overall quality of the equipment. Factors affecting the quality of electroplating include internal factors and external factors. Therefore, it is not only necessary to have a comprehensive understanding of the internal factors that affect the quality of electroplating, but also the external factors that affect the quality of electroplating should not be ignored. Strict control of each link can ensure the quality of electroplating.
The factors affecting the quality of electroplating include two aspects: internal factors and external factors:
1. Internal Factors
Strict quality management in the electroplating workshop is a powerful guarantee for the quality of electroplated parts. In order to fundamentally improve the quality of electroplating and obtain high-quality coatings, there should be a comprehensive understanding of every internal link that affects the quality of electroplating.
(1) Pre-processing Factors
The bonding force, anti-corrosion performance and appearance quality between the plating layer and the substrate are directly related to the quality of the surface treatment before plating. Oil, rust, oxide scale and other dirt attached to the surface of the part are intermediate obstacles that prevent the electroplating solution from fully contacting the metal substrate. It is impossible to form a qualified electroplating layer on this surface. When an extremely thin oil film and oxide film are attached to the plated parts, even though the coating has a normal appearance and fine crystallinity, the bonding strength is greatly reduced.
Therefore, the pre-treatment of the parts is a prerequisite for obtaining good results in the entire electroplating process. First of all, the concentration and purity of the degreasing and pickling solution must be ensured. The floating oil in the solution must be cleaned up in time; secondly, when the rust removal solution reaches a certain amount of impurities, it will affect the quality of the coating, so it must be replaced regularly.
(2) Electroplating Chemical Factors
In electroplating production, various harmful impurities enter the electroplating solution due to various reasons. There are many types of impurities, roughly including metal impurities, metal oxides, non-metal impurities, various insoluble suspended solids, and organic impurities. The types of impurities contained in various plating solutions are not the same, and the tolerance to the same impurity is also different. When one or several harmful impurities accumulate to a certain extent, it will affect the performance of the plating solution and the quality of the coating. Therefore, it is not necessary to wait for the accumulation of impurities to cause harm before disposing of the electricity.
Plating solution. In addition, the content of each component of the electroplating solution has an optimal process range, and the tank solution should be tested and analyzed regularly to ensure that each component is within the process range. At the same time, according to the production task volume, actual experience and test results, there is an accumulation of impurities. Before the quality of the electroplating layer may be affected, the electroplating solution should be purified to ensure the stability of the electroplating solution.
(3) Process Conditions Control Factors
The control of process conditions directly affects the quality of the electroplated layer. Only by mastering and controlling the various process conditions of each plating species, can we obtain high-quality plating. Process conditions such as temperature, current density, pH value, and plating time must be matched. For example, when hard chromium plating, the temperature and current density are not properly matched, which will have a great impact on the cathode current efficiency, dispersion ability, coating hardness and brightness of the chromium plating solution. As shown in the figure below, when the temperature is high, the current density needs to be increased appropriately to obtain the desired coating. The two restrict each other, change one, and the other factor must change accordingly. Therefore, if the process conditions are not well controlled, electroplating quality accidents will occur.
2. External Factors
As a part of the overall quality of product parts, the electroplating quality of parts is not only affected by the electroplating process and the internal links of the electroplating workshop, but also by other production links and production and technical departments of the enterprise to varying degrees. These factors are often very easy to be ignored. , We should have a comprehensive understanding of these factors.
(1) Design Factors
Product designers often only pay attention to the shape, size, processing accuracy and other factors of the product parts in the drawing design process of the parts, and do not consider much of the processing technology of the parts, especially the electroplating process, which brings a lot of unnecessary troubles to the electroplating work , At the same time, it also has a certain impact on the quality of the product.
1. The influence of part shape on the quality of electroplating.
The dispersing ability of the chromium plating electrolyte is extremely low. The current concentration in the corners and tips of the parts is easy to cause local defects such as burrs, scorching, and nodules. For parts with more complex shapes, the deep recesses and inner surfaces are often No plating, thus failing to achieve the desired effect. Although the use of pictographic anodes, protective cathodes and auxiliary anodes can obtain coatings with as uniform thickness as possible, this will inevitably bring great troubles to the electroplating work, and the cost of electroplating will greatly increase. Therefore, designers should consider comprehensively during the design process, and craftsmen should also strengthen process review. Only use pictogram anodes, protective cathodes and auxiliary anodes when absolutely necessary.
2. The influence of the assembly on the quality of electroplating.
The so-called assembly refers to a part that cannot be dismantled after being welded or riveted by multiple parts. For example, for some products, the velvet belt supporting plate combination of the upper, upper and lower cleaning devices of the suspended spindle series roving frame is an example. It is a complete set for electroplating. During the electroplating process, the chemical solution penetrates into the gaps of the parts. On the one hand, after the parts are placed for a period of time after electroplating, the electrolyte hidden in the gaps seeps out and reacts with the plating layer to cause the parts to rust. On the other hand, due to the infiltration of the chemical liquid, the chemical liquid of the previous process cannot be thoroughly cleaned, contaminating the chemical liquid of the next process, causing the chemical liquid to be contaminated and affecting the quality of electroplating. Therefore, in the design, it is necessary to avoid electroplating of the whole set of joints as much as possible, and consider as much as possible after the electroplating of individual parts, and then riveting or adopting other methods for fitting.
3. The drawing is not clearly marked.
Traditionally, the parts to be electroplated are simply indicated on the drawings, but the main electroplated surfaces are not clearly indicated, which makes the specific operation easy to cause confusion. For the main parts, the electroplating process must ensure the internal and external quality of the coating, and there should be no obvious chromatic aberration. Therefore, only when the main and minor parts are marked on the drawing, can the hanger be properly selected for electric shock during the electroplating process, and the mounting position of the parts can be determined, so that the main parts and the minor parts are taken care of, and the insulation protection is not plated. To ensure the quality of electroplating.
(2) Surface Factors Before Plating
The surface quality of parts before electroplating seriously affects the quality of electroplating. A coating formed on a flat and smooth surface is always better than a coating formed on a rough surface. Machining, cold drawing and other parts manufacturing processes before electroplating, only to ensure that the size, shape tolerance, surface finish, etc. processed in this process are qualified, and the rust, oxide scale, difficult to remove dirt, bumps, etc. on the surface of the parts will cause the parts after electroplating The appearance does not meet the design and use standard requirements. In addition, the surface state of some parts is inconsistent when entering the electroplating process. The same part has both precision-machined parts and parts with severe rust and scale, which makes pre-plating treatment impossible. Too short pickling time will cause oxidation. The oxide scale on the skin part cannot be removed and electroplating cannot be carried out. If the pickling time is too long, the precise size parts will be corroded and scrapped. The correct method should be to perform pretreatment such as sandblasting or pickling to remove the surface oxide scale on the material with severe corrosion and oxide scale, and then perform mechanical finishing to provide a surface that is as consistent as possible for the final electroplating treatment of the part.
(3) Factors Of Production Schedule
Because the processing procedures of many parts need to be transferred to multiple workshops, and electroplating is always the last process, often the parts have not arrived yet
In the electroplating workshop, the assembly workshop has already waited for the parts to be assembled. This situation causes the construction period to be too tight, and it is often continuous shifts to catch up with the construction period. It is easy to cause the electroplating time to fail to meet the process requirements, or the working light at night is not clear, which affects the electroplating quality. Therefore, the production department should coordinate the processing period of each workshop to achieve balanced production to ensure the processing time of the electroplating process to produce qualified electroplated products.
(4) Storage And Packaging Factors
Under atmospheric conditions, ferrous metals are coated with zinc to prevent corrosion. However, when the zinc coating comes into contact with phenolic paint, alkyd paint, phenolic plastic, damp wood, plywood, etc., the corrosion of the zinc coating is quite serious. The longer the time, the thicker the corrosion product. This is a small amount of organic volatile atmosphere. The acceleration of corrosion is called atmospheric corrosion. The substances that can produce such an organic volatile atmosphere are: paint, plastic, resin, wood, etc. The corrosion rate of atmospheric corrosion is closely related to the concentration of the organic volatile atmosphere. The higher the concentration, the more severe the corrosion. However, the organic volatile atmosphere can only corrode the zinc coating in a humid atmosphere. If there is only a corrosive atmosphere and the surrounding air is very dry, there will be basically no corrosion. Therefore, in the atmosphere, only when there is no organic volatile atmosphere or completely dry In air conditions, zinc coating is a reliable protective coating. In the storage process of qualified parts for electroplating, the environment of the warehouse must be ensured to avoid atmospheric corrosion of the parts. In addition, during transportation, product packaging directly affects the corrosion resistance of parts. Therefore, the source of organic volatile atmosphere must be minimized. Galvanized parts must be stored in wooden boxes, with reliable inner packaging and desiccant to ensure that the parts are completely isolated from the external corrosive atmosphere, otherwise the parts are very easy to rust , Affecting product quality and causing adverse effects. These external factors are very easy to be ignored by us and become an important factor affecting the quality of electroplating.
3. Conclusion
As a special type of work in the manufacturing industry, electroplating is indispensable, but it is often ignored. Once there is a quality problem, just look for the cause from the electroplating process, and ignore other external factors. Therefore, in order to ensure the quality of electroplating products, not only the electroplating workshop, but the entire quality control system must have clear responsibilities and authorities, as far as possible for the electroplating process, to provide a good substrate for the electroplating process. From drawing design to process and tooling preparation, from parts processing, assembly, inspection to transshipment and storage, to the final packaging and transportation, every link should be strictly controlled to ensure the quality of electroplating, which has very important practical significance for improving product quality.