What Does an Electroplater Do?

Electroplating is an electrochemical process

Classified by coating composition:

(1) Chrome plating.

Generally includes three stages of pre-plating, electroplating and post-plating.

The complete process:

1.Acid leaching All-plate electroplating copper Graphic transfer Acid degreasing Secondary countercurrent rinsing Micro-etching Secondary immersion acid Tinning Secondary countercurrent rinsing

2. Counter current rinsing pickling graphic copper electroplating secondary counter current rinsing nickel plating secondary water washing dipping citric acid gold plating recycling grade 2-3 pure water washing drying

Plastic shell plating process:

Chemical degreasing water washing dipping acetone water washing chemical roughening water washing sensitization water washing activation reduction chemical copper plating water washing bright sulfate copper plating water washing bright sulfate nickel plating water washing bright chromium plating water washing drying Dry check.

In the above process, the most prone to failure is bright sulfate copper plating. The phenomenon is poor deep plating ability, rough and rough, etc. The poor deep plating ability should be treated differently. If the low current area is not bright, but high The current region is very bright and it is white. You can consider whether N (ethylene thiourea) is too much. Adjust the method to add appropriate amounts of M (2-mercaptophenylhydrazone) and SP (

1. There should be good adhesion between the coating and the base metal, and between the coating and the coating;

2. The coating should be fine, smooth, and uniform in thickness;

3. The coating should have a specified thickness and as few pores as possible;

4. The coating should have the specified indicators, such as brightness, hardness, electrical conductivity, etc .;

5. The plating time and the temperature of the plating process determine the thickness of the coating. Ambient temperature is -10 60 ;

6. The input voltage is 220V ± 22V or 380V ± 38V;

7. The maximum working noise of water treatment equipment should not be greater than 80dB (A);

8. Relative humidity (RH) should not be greater than 95%;

9. The COD content of raw water is 100mg / L 150,000mg / L.

(1) Main salt system

Each plating type will develop a variety of main salt systems and matching additive systems. For example, galvanization includes cyanide zinc plating, zincate zinc plating, chloride zinc plating (also known as potassium salt zinc plating), Ammonia zinc plating, sulfate zinc plating and other systems.

Each system has its own advantages and disadvantages, such as good dispersibility and depth of cyanide galvanizing solution, fine coating crystals, good bonding with the substrate, good corrosion resistance, wide process range, stable and easy operation of the plating solution. Too sensitive and other advantages. But highly toxic and seriously pollutes the environment. Chloride zinc plating solution is a single salt plating solution without complexing agent, and the wastewater is easy to handle; the brightness and leveling of the coating are better than other systems; the current efficiency High, fast deposition speed; steels with low hydrogen overpotential such as high carbon steel, castings, forgings, etc. are easy to plate. However, due to the weak acidity of chloride ions, it has certain corrosiveness to the equipment, on the one hand, it will cause certain corrosion to the equipment On the other hand, such plating solutions are not suitable for deep holes or tubular parts that need auxiliary anodes.

(2) Additives

Additives include gloss agents, stabilizers, softeners, wetting agents, low-zone dislocation agents, etc. The gloss agents are divided into main gloss agents, carrier brighteners and auxiliary gloss agents. For the same main salt system, use different manufacturers The quality of the resulting coatings is very different. Generally speaking, the additives in developed countries such as Europe, America, and Japan are the best, followed by Taiwan, and the mainland production is relatively inferior to the first two.

The combination of the main salt and the additives of a specific manufacturer determines the overall performance of the plating solution used. Excellent additives can make up for the lack of some properties of the main salt. For example, the excellent chloride zinc plating additive and the main chloride salt are combined The deep plating ability of the bath is better than that of many cyanide zinc baths.

(3) Plating equipment

Hanger: Use the square hanger with the square plating tank, the round hanger with the circular plating tank. The round plating tank and hanger are more conducive to ensuring the uniform current distribution, and the square hanger needs to be added around the hanger. Provide a current-distribution device such as a barbed wire or shorten the length of the anode plates on both sides, and use an oval anode arrangement as shown in the figure.

Stirring device: Promote the flow of the solution, make the solution state evenly distributed, and eliminate the stay of air bubbles on the surface of the workpiece.

Power supply: DC, good stability, small ripple coefficient. ^[3]

Pre-treatment-chemical cleaning. According to the type and properties of oils and fats, the degreaser contains two main components, an alkaline builder and a surfactant.

1. Alkali substances. Alkali builders are commonly used sodium hydroxide, soda ash, sodium silicate and sodium tripolyphosphate. As the alkaline agent, sodium hydroxide and soda ash are the cheapest and the wastewater is difficult to treat. Sometimes the cleaning object is damaged due to the strong alkalinity. On the other hand, sodium hydroxide and soda ash have no emulsification effect on mineral oil cleaning.

Sodium silicate and sodium tripolyphosphate can provide both alkalinity and a certain emulsifying power. They are widely used in various degreasing and cleaning agents, especially alkali-sensitive degreasing processes. The biggest disadvantage of using sodium silicate is that if it is washed without hot water after degreasing, it is difficult to completely wash the residual sodium silicate directly by cold water washing. The residual sodium silicate will react with the acid of the next process to form a strong adhesion. Silica, which affects the adhesion of the coating; sodium tripolyphosphate is mainly concerned about phosphorus pollution and environmental damage.

2. Surfactant. Surfactants are the core components of degreasers. Early degreasers were mainly emulsifiers, such as fatty alcohol polyoxyethylene ether (AEO) series, alkylphenol polyoxyethylene ether (TX, NP ) Series and so on. Excessive use of emulsifiers will emulsify and solubilize the oil that has fallen off and solubilize it in the working fluid, resulting in a gradual decline in the degreasing ability of the working fluid, which requires frequent replacement of the working fluid.

However, as the price of surfactants rises, it is increasingly required to reduce the amount of surfactants used and increase the rate of degreasing. This requires that the degreasers have good dispersion and resistance to secondary deposition, and the oil will fall off. It is peeled from the metal surface and does not emulsify or saponify in the solution, but only floats on the surface of the solution, keeping the tank liquid clear and continuous degreasing ability.

On the other hand, surfactants suitable for degreasing are generally non-ionic products. Non-ionic products are generally more expensive. In order to reduce the cost of degreasers, anionic products will also appear in some degreaser formulations. It is a nonionic surfactant fatty acid methyl ester ethoxylate sulfonate (FMES) with non-ionic properties. It has excellent "dispersion and roll-off" characteristics, which is helpful for non-emulsification peeling and removal of oils. ^[3]

The product pre-treatment process for electroplating is very important. The general traditional process uses acid liquid to treat the workpiece, which has a serious environmental pollution and a poor working environment. At the same time, the biggest disadvantage is that it is difficult to remove the residual acid after pickling and rusting of complex parts. Rinse well. After the workpiece is electroplated, the time is not long. Corrosion occurs along the gap, which damages the surface of the plating layer and seriously affects the appearance and internal quality of the product. After the ultrasonic cleaning technology is applied to the pre-plating treatment, not only the dirt on the surface and the gap of the object can be quickly peeled off, but also the sprayed layer of the electroplated parts is firm and will not return to rust.

Utilizing the cavitation effect produced by the ultrasonic wave in the liquid, the oil contamination on the surface of the workpiece can be washed away. With appropriate cleaning agents, the surface of the workpiece can be quickly cleaned.

Electroplating process requires higher surface cleanliness, and ultrasonic cleaning technology is an ideal technology to achieve this requirement. Using ultrasonic cleaning technology, it can replace the solvent to clean the oil; it can replace the electric degreasing oil; it can replace the strong acid etching to remove the rust and scale on the surface of carbon steel and low alloy steel.

For several common workpiece surface conditions before electroplating, the process of ultrasonic cleaning is introduced:

1. Cleaning of polishing paste on the surface of polishing parts: In general, polishing paste is often blended with paraffin wax. Paraffin wax has a large molecular weight, a high melting point, and is solid at normal temperature. It is a difficult substance to clean. The traditional method is to use organic solvents for cleaning. Or boiling in hot alkaline water has many drawbacks. With ultrasonic cleaning, a water-based cleaning agent can be used. Under moderate temperature conditions, the surface of the workpiece is thoroughly cleaned in a few minutes. The common process is: soaking ultrasonic cleaning rinse with clean water (purified water).

2. Cold-rolled steel plate with oil and a small amount of rust on the surface: The surface of the cold-rolled steel plate is generally oily, dirty, or with a small amount of rust. It is easier to clean, but after cleaning by ordinary methods, a very thin floating layer remains on the surface of the workpiece. Ash, which affects the subsequent processing quality, and sometimes has to use strong acid soaking to remove this layer of floating ash. By using ultrasonic cleaning and adding a suitable cleaning solution, the surface of the workpiece can be cleaned quickly and conveniently, and the surface of the workpiece can be highly active, and the process of acid leaching activation before plating can sometimes be eliminated.

3. Workpieces with oxide scale and yellow rust on the surface: The traditional method is to soak and clean with hydrochloric acid or sulfuric acid. Such as the use of comprehensive ultrasonic treatment technology, you can quickly and simultaneously remove oil and rust on the surface of the workpiece in a few minutes, and avoid the hydrogen embrittlement problems associated with strong acid cleaning.

After plating, various treatments are applied to the plating layer to enhance various properties of the plating layer, such as corrosion resistance, resistance to discoloration, and solderability.

Dehydration treatment: add dehydrating agent in water, such as bright nickel plating after treatment.

Passivation treatment: improve the corrosion resistance of the coating, such as galvanizing.

Anti-tarnishing treatment: Add anti-tarnishing agent in water, such as silver plating, tin plating, gold-plated imitation, etc.

Improving solderability processing: such as tin plating, so the quality of the post-processing process directly affects the quality of these coatings. ^[2]

There are several general indicators used to evaluate any electroplating process, which are usually divided into indicators related to the performance of the plating solution and indicators related to the performance of the coating. The plating solution index is the main index of the electroplating process, including the current efficiency of the plating solution (related to the deposition speed), the dispersion ability, the deep plating ability, the crystalline state of the plating layer, the stability of the plating solution and the operability (including the control of process conditions, Are there any special requirements for equipment), the degree of impact on the environment, economic benefits (plating processing costs), etc.

The performance index of the coating is an index of the performance and quality of the coating guaranteed by the electroplating process. It is an important index for intuitively evaluating the level of the electroplating process, such as the decorative performance, brightness, corrosion resistance, brittleness, and porosity of the coating. Functional coatings should be added with functional performance indicators, such as electrical conductivity, reflected light coefficient, solderability, wear resistance, and so on.

These two types of indicators belong to advanced technology with high level. Sometimes, the technology with good performance of the plating solution may not have good coating index; while some technology with good coating index, the performance of the plating solution is not good. People usually judge and select the plating process based on the coating index. That is to say, in order to obtain a good plating layer, it is sometimes necessary to use a plating solution with poor plating performance, such as decorative chromium plating. Many cyanide plating is also a plating type with good coating performance but great environmental impact.

Because process management directly affects production efficiency and product cost. Therefore, the management of process parameters must be reasonable, the management is not good, and the plating solution will be shut down frequently, which is a great waste. However, excessive management will increase management costs and increase the extra consumption of resources. These parameters can be divided into two categories by the composition of the plating process parameters. One is the relatively fixed factors once set in the process of setting up the production line, like congenital factors. Unless there is a failure, the changes will not be large. For example, The waveform of the rectified power supply, the speed of the cathode movement, the flow rate of the filter, the size and structure of the plating tank, etc. These parameters must be controlled at the design stage and leave room for them; the other is that fluctuations often occur in electroplating production The parameters must be adjusted at any time through monitoring. The management of process parameters in production refers to the management of such variable parameters.

However, in the practice of electroplating production management, it is normal to loosen variable process parameters. Many plating solutions are in a sub-health state like humans, and barely maintain production, and problems will occur over time. For example, the anode area of many companies is often in an inadequate state, because the purchase of anode metal materials is not timely, there is almost no inventory, and the cost is high, which has become an object that enterprises can save.

The elements of the daily management of the variable parameters of the electroplating process are mainly the following.

(1) Temperature management. The effect of temperature on electroplating has been described in detail previously. Temperature has important effects on the quality of electroplated surfaces and the efficiency of electroplating. Therefore, all plating types that need to be heated should have constant temperature controlled heating equipment and require employees to make temperature records of the plating solution. Of course, from the perspective of energy conservation, room temperature processes should be used as much as possible. However, some plating types can only work at a certain high temperature. The key is to strengthen management to prevent waste of energy and plating solution caused by overheating.

The temperature management is not limited to the plating tank, and the temperature of hot water washing should also be managed. Many electroplating companies only pay attention to the temperature control of the plating tank, regardless of hot water, either insufficient heating or excessive heating, which is detrimental to quality and wastes resources.

(2) pH management of plating solution. The pH value of the plating solution is a relatively hidden change factor, and it is often found when something goes wrong. Therefore, it is absolutely necessary to constantly check the pH of the plating solution. For more demanding plating, it is best to use a digital pH display controlled by a sensor. In this way, the pH value of the bath can be known in time. The easiest way is to use a precision test paper to measure in the field. Let the operator also have test strips available. Don't have test strips only for craftsmen. This can ensure that the pH of the plating solution is in a state monitored by more people.

(3) Composition management of plating solution. The management of the bath composition is mainly obtained by chemical analysis. This problem is easier to handle if you have an organization that has its own chemical analysis department. It is enough to take regular sample tests.

Electroplating companies without their own analysis room, because it is troublesome and costly to go out for analysis with the plating solution, the analysis period of the plating solution is set to be very long, exceeding the normal analysis time. The composition of the plating solution is out of order, and the feed is often analyzed only when something goes wrong. Therefore, based on the frequency of production and the consumption of materials, or based on the area to be plated, the basic law of the composition of the plating solution is measured to periodically analyze the plating solution. When the processing volume is large, every two days It is necessary to analyze once. When the processing volume is small, it must be analyzed at least once a week. At the same time, the craftsman must periodically perform a Hall tank test on the plating solution to determine that the plating solution is in the optimal process range. Hall groove test is not only an important tool for the development of electroplating processes, but also an important means for the management of electroplating sites.

There are also lead plating, iron plating, silver plating, gold plating, etc. Electroplating alloys include: copper-based alloys, zinc-based alloys, cadmium-based, indium-based alloys, lead-based, tin-based alloys, nickel-based, cobalt-based alloys, and palladium-nickel alloys. In terms of composite plating: nickel-based composite plating, zinc-based composite plating, silver-based composite plating, diamond-inlaid composite plating ^[2]