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Two factors affecting the quality of electrodeposited coatings are discussed
Release time:2020-03-11 14:49   Read the number:423time  

The quality of electroplated parts directly affects the overall quality of the equipment. The factors affecting the quality of electroplating include internal factors and external factors. Therefore, not only to affect the plating quality of the internal factors should have a comprehensive understanding, and to affect the plating quality of external factors can not be ignored, strict control of each link, to ensure the plating quality.

The factors affecting the quality of electroplating include internal factors and external factors:

I. internal factors

Strict quality management in electroplating workshop is a strong guarantee for electroplating parts quality. In order to improve the quality of electroplating fundamentally and obtain the purpose of high quality electroplating, every internal link that affects the quality of electroplating should have a comprehensive understanding.

(I) pretreatment factors

The adhesion, corrosion resistance and appearance quality of coating and substrate are directly related to the surface treatment of parts before plating. The dirt attached to the surface of the parts, such as oil, rust, oxide skin, is the intermediate barrier that hinders the full contact between the electroplating solution and the metal substrate, and it is impossible to form a qualified electroplating coating on the surface. When the plating is attached to very thin or even invisible oil film and oxide film, although the appearance of normal, crystal fine coating, but the bonding strength is greatly reduced.

Therefore, the pretreatment of parts is a prerequisite for good results in the whole electroplating process. First, the concentration and purity of oil removal and pickling solution must be guaranteed. Secondly, the rust removal liquid impurities reached a certain amount, will affect the quality of the coating, so to replace regularly.

(2) factors of electroplating solution

In electroplating production, due to various reasons, lead to a variety of harmful impurities into the plating solution. There are many kinds of impurities, such as metal impurities, metal oxides, non-metal impurities, insoluble suspended matter and organic impurities. The kinds of impurities contained in various plating baths are not the same, and the tolerance of the same kind of impurities is not the same. When one or more harmful impurities accumulate to a certain extent, the performance of the plating solution and the quality of the coating will be affected, therefore, it is not possible to wait for the accumulation of impurities to cause harm, before the treatment of electricity

Plating solution. In addition, there is an optimal process range for each component content of electroplating solution. The tank solution should be analyzed regularly to ensure that each component is within the process range. At the same time, according to the production tasks, practical experience and test results, before the accumulation of impurities may affect the quality of electroplating, the plating solution purification treatment, in order to ensure the stability of electroplating solution.

(3) control factors of process conditions

The control of process conditions directly affects the quality of electrodeposit. Only by mastering and controlling the process conditions of each type of plating, can we obtain high quality coating. Temperature, current density, pH value, plating time and other process conditions must match. If the temperature and current density are not properly matched during hard chromium plating, the cathode current efficiency, dispersing ability, hardness and brightness of the coating will be greatly affected. As shown below, when the temperature is high, it is necessary to increase the current density appropriately to obtain the required coating. Both restrict each other, change one, the other factor must change accordingly. Therefore, if the process conditions are not well controlled, electroplating quality accidents will occur.

Second, external factors

Parts of electroplating quality as a link, the overall quality of product parts not only affected by electroplating process and electroplating workshop internal links, but also by other manufacturing enterprises in different degrees and production department, technical department, the influence of these factors are very easy to be ignored, we should have a comprehensive understanding of these factors.

(I) design factors

Product designers in the drawing design process of parts often only pay attention to the shape, size, processing precision and other factors of the parts, the processing process of the parts is not considered much, especially the plating process, which brings a lot of unnecessary trouble to the plating work, and also has a certain impact on the quality of the products.

1. Influence of part shape on plating quality.

The dispersing ability of the chrome-plated electrolyte is very low, and the current is concentrated in the corners and tips of parts, which is easy to cause local defects such as burr, scorch and nodules. For the complex shape of the parts, its deep concave and inner surface often can not get the coating, so as not to achieve the expected effect. Although pictographic anode, protective cathode and auxiliary anode can be used to get the thickness of the coating as uniform as possible, but this will bring great trouble to the plating work, and the cost of plating will increase greatly. Therefore, designers should take comprehensive consideration in the design process, and technicians should also strengthen the process review. Pictographic anodes, protective cathodes, and auxiliary anodes are used only as a last resort.

2. Influence of composite parts on electroplating quality.

The so-called assembly refers to a number of parts after welding or riveting into an undetachable parts. Such as some products, hanging ingot series roving frame, upper, lower cleaning device of the belt plate joint is this example, it is a complete set of plating. In the process of electroplating, the medicine solution penetrates into the gap of parts. On the one hand, after the parts are placed for a period of time after electroplating, the electrolyte hidden in the gap oozes out and reacts with the coating to cause corrosion of parts. On the other hand, due to the penetration of the liquid, the liquid of the previous process cannot be thoroughly cleaned, contaminating the liquid of the next process, resulting in the contamination of the liquid and affecting the quality of electroplating. Therefore, in the design, should try to avoid the whole set of combined parts for electroplating, as far as possible to consider a single part after electroplating, then riveting or other methods to cover.

3. The drawing is not clearly marked.

Customarily, the parts to be electroplated are simply indicated on the drawing, and for what is the main electroplating surface, do not clearly indicate, this makes the specific operation is easy to cause confusion. For the main parts, the plating process must ensure the inner and outer quality of the coating, no obvious color difference. Therefore, only in the drawing marked out the main part and the secondary part, electroplating process can be properly selected hanging electric shock, determine the parts of the mounting and hanging position, to take care of the main part, take care of the secondary part, insulation protection not plating part, in order to ensure the quality of electroplating.

(2) surface factors before plating

The surface quality of parts before electroplating seriously affects the quality of electroplating. Coatings formed on leveling smooth surfaces are always superior to coatings formed on rough surfaces. Before electroplating, machining, cold drawing and other parts manufacturing processes, only to ensure that the process of the size, shape and position tolerance, surface finish and other qualified, and parts surface rust, oxidation, difficult to remove dirt, bump, will lead to electroplating parts appearance can not meet the design standard requirements. In addition, the parts surface state when it enters the electroplating process, both the same parts processing precision parts, and there are serious corrosion and scale of the site, prevented plating pretreatment, acid pickling time too short can make a scale parts scale can't without the plating, acid pickling time is too long can make precision parts corrosion scrap. The correct method should be the serious corrosion and oxidation skin of the material for sand blasting or pickling and other pretreatment to remove the surface of the oxidation skin, and then the mechanical finishing, for the parts of the final electroplating treatment to provide a can

Can be consistent with the surface state, to prevent the plating process to take care of one.

(3) production schedule factors

Because the processing process of many parts needs to cross several workshops, and electroplating is always the last process, often the parts have not yet arrived

Reached the plating workshop, the assembly workshop has such parts assembled. This kind of circumstance causes time limit for a project to be too tight, often it is even a shift to add a point to be in a hurry time limit for a project, cause electroplating time to be short of craft requirement easily, or night work light is not beautiful not clear, affect electroplating quality thereby. Therefore, the production department should coordinate the processing period of each workshop to achieve balanced production, in order to ensure the processing time of the electroplating process, in order to produce qualified electroplating products.

(4) storage and packaging factors

In atmospheric conditions, ferrous metals are coated with zinc to prevent corrosion. But when zinc coating in contact with phenolic paint, alkyd paint, phenolic plastic, wet wood, plywood, etc., the corrosion of zinc coating is quite serious, the longer the time the corrosion product is thicker, this is a small amount of organic volatile atmosphere on the atmosphere of corrosion acceleration, called atmosphere corrosion. Can produce such organic volatile atmosphere of the material: paint, plastic, resin, wood, etc. The corrosion rate of atmospheric corrosion is closely related to the concentration of organic volatile atmosphere. The higher the concentration, the more serious the corrosion. Organic volatile atmosphere, however, only in the humid atmosphere, to corrosion of the zinc coating, if only the corrosive atmosphere, and ambient air is very dry, is basically don't appear corrosion phenomenon, in the atmosphere, therefore, only when there is no organic volatile atmosphere or completely dry air condition, the zinc coating is the reliable protective coating. During the storage of qualified parts, the environment of the warehouse must be guaranteed to avoid the corrosion of parts. In addition, in the process of transportation, product packaging directly affects the corrosion resistance of parts. Therefore must minimize the source of organic volatile atmosphere, galvanized parts must be packed with wooden case storage, to add reliable packaging, and put into the desiccant, in order to ensure that the parts and the external corrosion atmosphere is completely isolated, otherwise the parts are very easy to rust, affect product quality, resulting in a bad impact. These external factors are easy to be ignored by us and become important factors affecting the quality of electroplating.

Three, endnotes

Electroplating, as a special kind of work in manufacturing industry, is indispensable but often neglected. Once there is a quality problem, just from the plating process to find the reason, and ignore other external factors. Therefore, in order to ensure the quality of electroplating products, not only the electroplating workshop, the entire quality control system, should have clear responsibility and authority, as far as possible for the sake of electroplating process, for electroplating processing to provide a good substrate. From drawing design to process, tooling preparation, from parts processing, assembly, inspection, transfer, storage, until the final packaging transportation, each link should be strictly controlled, to ensure the quality of electroplating, which is of great practical significance to improve product quality.

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