Polishing is a process due to which all impurities and irregularities are removed from the metal surface and it again acquires its original luster.
Execution methods
Currently, we can distinguish several of the following types of grinding of metal surfaces:
- The first and most simple and common method is manual polishing. Most often, this method is resorted to when carrying out repairs at the facility.
- The following method is already more professional and is called semi-mechanical grinding. This method is carried out using a polishing machine, on which special polishing wheels are put on.
- The third method is machine. It is used in large industrial enterprises. All grinding operations for metal products are performed by machines in automatic mode.
- The last type is waterjet grinding carried out on special machines. This method is used only if the volume of metal products in need of processing is quite large. It is worth adding that plasma as well as chemical-mechanical treatment are carried out according to the same principle.
Tools and Polishing Methods
The polishing process is an action that requires certain tools. Moreover, depending on the method of performing this operation, the used inventory also changes. The most commonly used tools are:
- polishing machine;
- Grinder;
- electric sharpener;
- drills with a clamp.
It is worth highlighting the mechanical method of surface treatment, as it has several advantages. The first plus, which is worth noting, is the ability to control the frequency of rotation of the circles of the machine. This has a positive effect on the entire process of processing a metal surface. Polishing is a very delicate process, and therefore, for example, polishing machines can be equipped with a wide variety of nozzles. The material from which these additional elements are made can be wool, leather, fabric.
Special processing method
Surface polishing can be done using combined methods. The combination of several processing methods is most often required when the metal surface is not prepared for work, and is also characterized by the presence of a rough surface. With such shortcomings, most often, before proceeding with polishing, a long-term electrolyte-plasma preparation is carried out. During this stage, a large amount of metal is removed.
It is worth noting that this is the method of processing the product that is used in the most extreme case, when it is necessary to restore the gloss of the metal coating in a very short time. The disadvantages of this particular processing process include the fact that the energy consumption at the initial stage is 100% higher than when processing with other methods. It can be added that polishing takes place in two stages: on the first, the surface is degreased, but on the second, grinding itself begins.
Manual polishing
Today, there are various materials for polishing, which will help restore the original shine of a metal surface without the use of any special machines. There are three groups of such substances.
The first includes water pastes. Such substances do not contain fats in their composition, but at the same time they cope with the tasks of cleaning the metal surface from pollution.
The second group is organic matter. The composition of these pastes includes paraffin, as well as several different oils. In addition, such products are further diluted with other types of oils or fatty acids before use.
The third group is diamond pastes, which are now considered a revolutionary solution. Tools from this category are able to quickly and effectively clean any metal surface from any contamination.
Diamond paste polishing
Diamond paste is very suitable, for example, for polishing machines. In order to successfully complete the operation, you must have lapping and several tubes of paste. To start work, it is necessary to apply the paste in a uniform layer on a rag or any other working surface of the subject, which will be polished. During practical tests, it was found that in order to achieve greater efficiency of polishing with diamond paste, it is worth adding olive or castor oil to it. During the same tests, it was found that the best ratio of paste and oil would be 40 and 60%, respectively. After the mixture has been diluted, it must immediately be applied to the surface to be polished. Recommendations from experts suggest that it is best to start working with larger grains, and then gradually switch to abrasive products.
Grinding or polishing?
Nowadays, many people, when they say "grinding" and "polishing", mean the same thing. However, these two operations have slightly different goals, that is, they mean not the same thing.
When talking about grinding a metal surface, it means that the surface cleanliness and its luster will be achieved by removing a thin layer of metal. For this, the rough grinding method is most often used. An element subject to this method of cleaning will be really clean as a result, but to see a reflection in it, for example, will be impossible.
The polishing process removes the smallest bumps in the surface, making it perfectly smooth. In the process of this type of work, a very small amount of metal is removed. The result that high-quality polishing will give is so brilliant that it will be almost impossible to notice the difference between it and the use of grinding.
Chemical polishing
The implementation of chemical polishing of the surface is carried out by the action of the solution on the metal. There it is combined with galvanic vapors, which forms a passivating oxide film on the surface of the product. As a result of using this method, you can get rid of the smallest microroughness on the surface of the metal, give it a shine. This happens simultaneously with how the top layer of the element dissolves.
It is important to note here that the quality of polishing using this method greatly depends on the speed with which the film was formed and the speed with which it dissolved in water. The best result, that is, the best gloss of a metal surface can be achieved if the minimum film thickness is achieved, and at the same time it should be enough to prevent the etching effect of the metal. To achieve this result, it is necessary to balance the rates of formation and washing off of the oxide surface.
Electrochemical method
Electrochemical polishing is a process that results in a decrease in the surface roughness of a metal and a specular gloss appears. In order to implement this process, it is necessary to place the part, which is the anode in this situation, in a bath with a substance called an electrolyte. By anode is meant an electrode that connects to the positive pole of a current source. Since a second electrode is needed to carry out the polishing process, cathodes made of copper are used as this consumable element.
Since the composition of the electrolyte is selected according to a special scheme, and the conditions for the entire process are also created in advance, it is possible to carry out electrochemical polishing in an uneven way. This allows you to dissolve first those places that are the strongest. Thanks to this, it is possible to eliminate roughness at the same time as creating the perfect shine on a metal surface.