Copper coating is the process of applying a layer of copper on the surface of various metals (aluminum, steel, nickel, brass). Copper coating gives metals an external appeal that can be used in various design projects. Also, the copper layer is able to improve the electrical conductivity of metal products, which significantly increases the possibility of further surface treatment.
Anyone who is even a little familiar with the basics of chemical reactions can master the technology of aluminum copper plating at home.
History of the discovery of copper
Copper is the first metal that obeyed man and played the most important role in the history of the development of civilization. This event took place several millennia BC, and the exact date of the start of use of this unique metal could not be established.
In ancient times, copper nuggets were used mainly to create weapons and household tools. Red-green metal nuggets were initially used in the same way as ordinary stones. Later, experimentally, people noticed that the processing of this material with a hammer gives it special properties. So the cold forging of metal was born.
Even later it was discovered that the metal melts and after cooling takes on other forms and properties. This stage was the beginning in the development of hot forming of metals.
Characterization and composition of copper
Copper is a heavy metal of pink-red color, which is highly soft and melts at a temperature of more than 1080 ℃. The electrical conductivity of the copper coating is 1.7 times higher than that of aluminum. Also, copper has a high thermal conductivity.
Many specific properties of the metal are due to the presence of various impurities in its composition. So, according to oxygen, which is in the composition of copper, the metal is divided as follows:
- copper without oxygen contains less than 0.001% impurities;
- refined copper contains oxygen of 0.001-0.01%;
- Pure copper contains about 0.03–0.05% oxygen;
- General purpose copper has 0.05–0.08% oxygen in its composition.
The presence of lead or bismuth in copper reduces the plasticity properties of the material. Sparingly soluble impurities (sulfur, lead, bismuth) increase the brittleness of the metal.
In the process of electrolysis, in addition to oxygen, hydrogen can enter the composition of copper alloys.
The main quality of copper is low resistivity and, as a result, high electrical conductivity. An increase in the impurities of various metals in a copper alloy significantly reduces the electrical conductivity of the material.
The high thermal conductivity of pure copper is significantly reduced when various alloying substances are added to its composition.
Also often used in industry are copper products that are highly resistant to corrosion in various environments except organic acids, ammonia and ammonium salts. An increase in the amount of impurities in the composition of copper leads to a significant decrease in the corrosion resistance of alloys.
The practical application of metal copper plating
The copper plating procedure of aluminum and other metals has a fairly wide practical application not only in domestic use, but also on an industrial scale. On many metals, a copper coating can be applied both as a main independent layer and as a sublayer for effective adhesion of the next main coating to the base metal of the product.
In most cases, aluminum copper plating in home workshops is performed for the following purposes:
- decorating jewelry;
- protection of metal parts from corrosion and cementation;
- elimination of damage and surface defects of products with complex shape and relief;
- making copies of products made from various materials;
- creating contact pads for brazing aluminum without using an acid composition;
- preliminary preparation of the surface of parts before chrome plating, silvering, nickel plating.
Types of copper plating of a metal surface
The procedure of copper plating of aluminum at home is not difficult to perform on your own. It is not necessary to use special equipment and active chemicals. High-quality coating is ensured by strict adherence to aluminum copper plating technology and knowledge of the ongoing processes.
There are two main types of copper plating of metal surfaces:
- With immersion of the workpiece in an electrolyte, in which the product is partially or completely immersed in a bath with a chemical reagent. The use of this method is justified in the case when it is required to apply a layer of copper evenly on the entire product.
- Copper plating without immersing the part in a chemical solution. This method is more complicated in execution. Using it is very effective if you want to copper-plating a certain area of the product.
In both of these cases, the activation of the substance for chemical copper plating of aluminum is carried out electrically, which requires the use of a constant voltage source.
Immersion Coating Equipment
For the high-quality performance of technological operations of aluminum copper plating, it is necessary to prepare simple equipment. Appropriate tools and materials can be either purchased on a retail network or made independently.
To perform the work, the following materials and devices will be needed:
- A 6-8 volt DC power supply unit having a continuous current control device and an ammeter. If there is no adjustment, it is advisable to include a rheostat and an ammeter in the circuit. They will be needed to control the process. If there is no stationary power supply, then a Krona type battery can be used.
- A special bath made of a material that is not subject to electrolytic effects (glass, plastic). The dimensions of the container are selected in accordance with the dimensions of the workpiece.
- Copper electrodes, which serve to supply electric current to the electrolyte during aluminum copper plating, and also make up for the loss of metal during the reaction.
- Electrolyte, the composition of which depends on the material of the initial billet.
Preparation of a solution for copper plating
Finding a ready-made solution for copper plating in aluminum is difficult. Typically, manufacturers allow the sale of the finished substance after the presentation of the relevant documents. Therefore, most people make their own solution for copper plating of aluminum at home from copper sulfate.
For these purposes, you will need:
- copper sulfate;
- distilled water;
- hydrochloric acid.
Prepare a solution only with the correct observance of the recipe. For this, copper sulfate (20 g) must be dissolved in 1 liter of water. Then add a small trickle of 2-3 ml of acid. The composition is thoroughly mixed until all crystals are completely dissolved.
The finished electrolyte for copper plating of aluminum with copper sulfate should be odorless and have a bright blue color.
Immersion Copper Technology
Copper plating of aluminum metal by the method of complete immersion of a workpiece in an electrolyte is carried out according to the following technology:
- The surface of the workpiece is cleaned with sandpaper or a brush, then degreased in a hot solution of soda and washed under running water.
- Two electrodes are suspended in the prepared container, which are connected to the positive terminal of the power source.
- A workpiece is placed between the electrodes, which is connected to the negative terminal of the power supply.
- The prepared electrolyte is poured into the working tank. The solution level should be above the top edge of the electrodes.
- Using the adjustment device, the operating current value is set. The value of the parameter is carried out at the rate of 10-15 mA per 1 cm 2 the area of the workpiece.
- After 20 minutes, the power is turned off, and the workpiece is removed from the bath.
- The remaining electrolyte is washed off with water, and the part is dried.
The execution time of the process is indicated approximately, it can be visually controlled by the color of the coating and the uniformity of its distribution. The longer the power is connected, the thicker the copper plating layer will be.
Immersion Copper Units
Copper-plating work on metal billets without immersion in electrolyte is carried out on large products that cannot be completely immersed in the bath. Also, this method is more effective in the processing of individual parts of the product.
To perform the technological operations of copper plating without immersion in the electrolyte, the following devices will be needed:
- The brush for applying the chemical composition is made of stranded copper wire. For this purpose, you need to remove the insulation at one end of the wire, then slightly separate the individual conductors. To make it convenient to hold the brush, it is better to attach it to a wooden stick or pencil.
- It is better to put a workpiece for work in any container without high sides. It is convenient to use an ordinary porcelain or glass plate. In addition, you will need a container for electrolyte, in which the brush will constantly dip. For this purpose, you can use a glass.
- The power source does not differ in parameters from the power supply used in immersion technology.
Application of a copper layer without immersion
The technology for performing work on copper plating of aluminum without immersing the workpiece in the electrolyte is as follows:
- A brush prepared in advance is connected to the positive terminal of the power supply.
- An electrolyte solution, which is similar in composition to the composition used in the case of immersion of the part, is poured into a container for wetting the brush.
- The workpiece, previously peeled and defatted, is placed in an empty container. Using the connector, the part is connected to the negative of the power source.
- The brush is dipped into the electrolyte and found at the place where it is necessary to apply a copper layer. It is very important that the brush does not touch the surface of the part.
- After applying a layer of copper, the workpiece is washed under a stream of water and dried.
In the process of doing work, you need to ensure that there is always a layer of electrolyte between the workpiece and the brush. To do this, you need to constantly dip the brush into a container with a solution.
All work with chemicals and a source of electric current must be carried out in compliance with the necessary precautions.
Performing copper plating in a residential building is strictly prohibited. For these purposes, it is better to use the utility room, garage or workshop. Electrical equipment must be earthed.
To protect human health, the following recommendations must be followed:
- use a respirator to protect the respiratory system;
- so that chemicals do not get into the eyes, it is necessary to work with protective glasses;
- all work should be carried out in special clothing (rubber gloves, oilcloth apron, special shoes).
The process of coating aluminum products with a layer of copper is not particularly difficult even for a person who is little familiar with the course of chemical reactions. Buying or making the appropriate equipment will not cause any particular problems. But many products that seemingly have lost an attractive appearance will gain a second life.