Polishing metal parts. How to polish stainless steel to a mirror at home - methods and expert advice. Grinding Methods

Stainless steel items have become a part of our lives. These are interior elements for the street and at home, various dishes at home and much more. Stainless steel is an alloy of iron and carbon mixed with special elements. Steel acquires high resistance to negative environmental factors thanks to these elements. But under the influence of various factors, even such a durable metal can lose its original appearance. How to polish to a mirror shine? If such a need arises, then you have two options:

Contact a specialized company that provides this type of service.
Do it yourself at home.

Let's look at how to polish metal to a mirror shine with your own hands in different ways at home.

Polishing at home

You can also get a shiny and smooth stainless steel surface at home. There are several ways that will help us with this.

Preparation for polishing

First you need to clean the product properly. You can use dishwashing liquid for this:

Divorce detergent in the water.
Clean the stainless steel surface with soapy water.
Rinse and dry the product thoroughly.

Olive oil polishing

This method is suitable for polishing tarnished items. All you need is a little olive oil and a soft cloth or napkin:

Apply a little oil to the fabric and spread it so that the entire surface is covered with an oil film.
Press the cloth firmly onto the surface and polish the stainless steel product with smooth movements.

Important! Continue until you see a noticeable change in structure.

Now you need to remove the remaining oil. Napkins or a dry towel are suitable for this. Wipe the surface until it is completely dry.

Polishing with flour

How else can you polish metal at home? For these purposes, you can use flour, however, this method is more suitable for flat surfaces, for example, for pots, knives or a sink:

Sprinkle flour over the entire surface and spread it evenly over the metal.
Polish using a soft cloth in a circular motion.

Important! For greater effect, you can use an old toothbrush.

Shake off any remaining flour.

Chemical method

You can polish metal at home chemically. To do this you need to prepare a special liquid. There are several ways to do this:

For such a solution you will need 230 ml of sulfuric acid, 70 ml of hydrochloric acid, 40 ml of nitric acid. To 1 liter of solution you need to add 6 g of acid black dye, 10 g of wood glue and 6 g of sodium chloride. Bring this mixture to a temperature of 65-70 degrees and place your stainless steel items in there for 5 to 30 minutes.
The solution is prepared in the following ratios: phosphoric acid 20-30%, hydrochloric acid - 3-4%, nitric acid - 4-5%, methyl orange - 1-1.5%. Place the product for 5-10 minutes at a temperature of 18-25 degrees.
Per liter of composition there are 660 g of hydrochloric acid, 230 g of sulfuric acid and 25 g of orange acid dye. Heat the solution to a temperature of 70-75 degrees and place a stainless steel object there for 2-3 minutes.

Important! All these components are very aggressive, so it is necessary to ensure complete eye protection. hands, face and respiratory organs.

Polishing steps using chemical solutions the following:

Immerse the pre-cleaned stainless steel item in a container with a chemical solution.

Important! Adhere to a strict dosage of substances included in the solution to obtain the desired concentration.

The liquid must be stirred constantly.
After the expiration date, the product must be removed and the remaining reagents washed off with clean water.
Wipe the part with a cloth containing polish.

Under the influence of chemicals, all roughness will be eliminated and the product will acquire its original shine and radiant appearance.

Mechanical polishing methods

These polishing methods involve the use of tools and devices such as:

polishing machine;
grinder;
electric sharpener;
drill with lock.

Important! The method has a number of advantages. This is fast, efficient, you can change the rotation frequency of circles and belts, use additional attachments made of leather, fabric, wool and other materials.

The product for polishing metal to a mirror shine with your own hands depends on the brand of stainless steel:

Diamond paste performed best, but it has one significant drawback - quite high price.
If you don’t have one, then you can use GOI paste. It comes in four types, depending on the grain size.

Important! For manual grinding, you can use the same diamond paste or GOI paste. Its effectiveness depends on the quality consumables.

This is done as follows:

Apply a little product to the felt disc and add a few drops of machine oil to dilute the paste.

Important! For metal, it is best to use a coarse-grained paste.

Polish the surface in a circular motion, being careful not to rub too hard.
Do this until you are satisfied with the result.

Important! How can you polish a knife to a mirror shine at home? Such smooth metal surfaces are polished with an ordinary file - wooden beam, covered with fabric onto which polishing paste is applied.

Stainless steel care

Polished stainless steel looks very beautiful. To maintain it in this condition, special polishes are used. They are available in the form of concentrates and liquid emulsions. The polish is applied immediately after the polishing process is completed. Then periodically you need to apply polish to ensure that your stainless steel product nice view for a long time.

Metal polishing is necessary to improve appearance metal products and giving them higher consumer qualities. Polishing gives metal products a decorative shine; it is also used in preparing surfaces for electroplating. The following methods of polishing metal surfaces are widely used in industry:

Disadvantages of traditional types of metal polishing

The first three of the listed methods for treating metal surfaces have a number of application limitations. The main limitation for the series industrial enterprises is the impossibility of automation when using mechanical, chemical or electrochemical methods for processing the surfaces of products in large batches of mass production.

Difficulties in using traditional types of metal polishing have both economic and technological reasons. Economic difficulties are associated with the high cost of production robots and CNC machines. The technological reasons for the difficulties in using traditional types of metal finishing are associated with the difficulties of building a fully automated production process. The forced use of manual labor at the stage of polishing products, activating the surface or cleaning it does not allow for the smooth operation of industrial automated lines. Often due to the use of outdated metal processing methods production line takes the form of a conveyor, which significantly increases the cost of production and ultimately negatively affects the competitiveness of the products produced.

Comparison of types of metal polishing

	Mechanical polishing	Chemical polishing	Electro-chemical polishing	Electrolytic plasma polishing
Performance	Average	Low	Average	High
Geometry limitation	Simple profile	Complex profile	Complex profile	Complex profile
Change material	Susceptibility to foreign particle intrusion	Uneven processing, etching	Poor finishing of flat surfaces	It is possible to strengthen the material
Difficulty of processing	Average	Average	High	Average
Possibility of automation	No	No	Eat	Eat
Material costs	High	High	High	Low
Installation depreciation period	25 years old	5 years	20 years	25 years old
Occupied production pl.	Small	Average	Average	Average
Environmental friendliness	Low	Low	Low	High
Fire hazard	Low	High	Average	Low
Energy consumption	Average	Low	High	High
Worker qualifications	High	Average	Average	Average

Widespread introduction into industry of more productive electrolytic-plasma polishing of metal will eventually make it possible to replace the toxic electrochemical processing method almost everywhere. Its advantages, in comparison with other methods of surface polishing, are high productivity and efficiency, compliance with the environmental cleanliness of the environment, high quality and speed of operations, and low cost.

The electrolyte-plasma method of surface polishing is environmentally friendly and satisfies sanitary standards, no special treatment facilities are required to clean the spent electrolyte.

Methods for polishing a metal surface by combining various methods and types of surface treatment

Often products are polished without preliminary surface treatment with an unprepared, rather rough surface with a rough relief, which entails the need for long-term electrolyte-plasma treatment, which is accompanied by the removal of a significant layer of metal, and leads to excessive energy consumption.

In addition, in the process of processing a rough branched surface, a phenomenon is observed where the current density in the first stage of processing is sometimes twice as high as that in the final stage. This is due to the fact that the initial rough surface area in contact with the electrolyte is apparently twice as large as that obtained as a result of processing.

In practice, it is better to polish products in two stages: in the first stage, cleaning and degreasing the surface, and in the second stage, the actual polishing. Cleaning parts before polishing is necessary because when manufacturing metal products by casting, or during their heat treatment, even in neutral environments, it is not possible to completely avoid contact of the surface with an oxidizing environment (for example, air) in the area high temperatures when surface oxidation of the metal occurs. For the purpose of cleaning before polishing, the following types of surface treatment are used:

tumbling
underwater grinding
waterjet treatment
cast iron sand treatment
processing with corundum chips
ultrasonic treatment
chemical and electrical etching

Types of metal surface treatment after gas plasma cutting

Smoothing surface roughness obtained after such a popular type of metal plasma processing as gas plasma cutting does not necessarily need to be done by cutting off the protrusions. Pre-treatment can be carried out by surface plastic deformation. In some cases, mechanical methods of treating surfaces with pastes do not consist of cutting off protrusions, but of kneading them, for which purpose the pastes contain special lubricants, chemically active, surfactants that soften the surface and fine oxide particles, for example, inert chromium oxide.

Polishing of metal products using the electrolyte-plasma method with preliminary preparation

To save energy, it is advisable to use electrolyte-plasma polishing technology in two stages, when at the first stage the rough surface relief is smoothed using various energy-saving surface treatment methods, and then at the second stage, finishing short-term electrolyte-plasma polishing is used.

For example, when polishing parts made of stainless steel, which is ductile and quite soft, the following surface treatment methods can be used at the first stage:

sanding under a layer of water with waterproof sandpaper with a grain size of 50–80 microns
brushing with a hard wire brush
electroetching in a 10% solution of oxalic acid at a voltage of 12 V for 5–10 minutes with a current density of up to 2 A/cm 2
sandblasting with fine cast iron chips
bleaching etching in a solution of 25% sulfuric and 20% hydrochloric acid in a volume ratio of 3/1 at a temperature of 30–40°C for 3–5–10 minutes.

Subsequent electrolytic plasma polishing of products can be carried out in a 5% aqueous solution of ammonium sulfate at a temperature of 80°C.

Methods of metal processing before electrolytic plasma polishing

Methods of metal processing using stripping

If the initial sample, the surface of which is pre-treated with coarse sandpaper with a grain size of 500 microns, is polished to a mirror finish for 5–6 minutes with a layer of metal of 0.05 mm removed, then samples treated to a matte state with sandpaper with a grain size of 50–80 microns are polished in two times faster in less than 3 minutes, and at the same time a layer of metal with a thickness of only 0.02–0.03 mm is removed. Energy savings when using surface pre-treatment with sandpaper are about 40%.

Types of metal processing using brushing

Very effective too pre-processing metal brushes rough ground or chiselled surface. Apparently, the surface relief during such processing is leveled due to plastic deformation of the metal, and partly due to brushing, i.e. abrasion, scratching of metal. The oxide film is also removed, which prevents uniform polishing of the product in cases where it is welded or subjected to high-temperature heat treatment.

Metal processing methods using etching

Good results were obtained with chemical etching, especially of samples that were subjected to heat treatment, since in this case scale is formed on the steel, which is difficult to remove by electrolyte-plasma treatment for 15 minutes or more. Etching such samples in solutions of sulfuric and hydrochloric acids creates a rough, scale-free surface without defects. Subsequent treatment of the samples in ammonium sulfate at a voltage of 260 V for 4 minutes produces a shiny surface.

Polishing metal using an angle grinder

Polishing is a type of metal processing that returns shine to the metal surface. At the present stage, the following grinding methods are distinguished:

What tools and machines are used? Mechanical methods involve the use of the following tools and devices:

The action must be prolonged to be effective. Finally, a thorough rinsing and drying will return the copper to its shine. Even if you use specific and safe products, we recommend washing copper items with soapy water. Copper varnish will ensure durability. Corrosion stains can always be removed with a mixture of vinegar and salt or, conversely, with lemon juice. If there are burns on the bottom of the pot, a fine abrasive powder is ideal.

Brass is an alloy of copper and zinc that has always been widely used. It is found in handles, locks, handrails and more. If the brass is painted, it can be cleaned using very warm soapy water and then polished. Even more simple system, useful for small areas or areas that are difficult to reach, is to rub in a piece of lemon that has been soaked in salty hot vinegar. Cleaning will be great, but you will have to use other methods for polishing.

polishing machine;
grinding machine;
electric sharpener;
drills with clamps.

This finishing method has several advantages. Firstly, it allows you to change the rotation frequency of circles and belts, which has a positive effect on the quality of processing of the metal plane; secondly, additional attachments made of fabric, leather, wool, etc. can be installed on the polishing machine.

Just take care to use the products that are available in the market. There are many types and are suitable for this purpose. If the brass is painted, we recommend simply dusting and washing with warm, soapy water. You don't need to do this often, but be sure to dry thoroughly each time. If the paint gets damaged, you will need to use acetone and remove it completely. Then it would be wise to contact an expert for the necessary repainting. Also for silver and metal we will use procedures similar to those we have encountered so far.

Special grinding machine - angle grinder

Hand sanding differs from automated in that its effectiveness depends on the quality of consumable polishing materials. In manual finishing, diamond paste and additives based on chromium or iron oxide are used. Smooth metal surfaces are polished with an ordinary file - a wooden block covered with a cloth, onto which polishing paste is applied.

Creamy liquids are great to spread evenly on the surface to be buffed with a cotton ball. Then allow the treated surface to dry and wipe it with a soft cloth until all residues are removed. Then wash the object with soap and water and rinse under running water for each product.

Unfortunately, silver is a metal that oxidizes very easily, so some care is required to protect it more effectively. Especially if the object has engraved or carved parts, it is recommended to apply a special protective paint, which is available in a canteen or specialty store. Unusual objects can also be protected with a black cloth wrapped around the objects themselves to eliminate contact with air and lightweight or aluminum foil for home use.

Polishing metal with a special device

Combined processing methods

Metal polishing can be carried out using combined methods, in the case of an unprepared and rough surface with rough relief. In this case, a long-term electrolyte-plasma finishing is prescribed, which consists of removing a significant layer of metal.

Brass is often used as a material for jewelry, accessories, architectural elements and home decor. Recently, vintage and vintage styles fashion trends are taking over, and brass has returned - both to the wardrobe and to our home.

This metal alloy has a beautiful and soft shine, but due to the copper content it darkens, and if objects are exposed to too much moisture, a light darkness can appear. In some brass products this is a sought after effect, but in others the darkening makes it even worse.

This processing method is used in extreme cases when quick restoration of the shine of a metal product is required. Among the disadvantages of the technology, one should highlight the high energy intensity, especially at the initial stage of processing, when 100% more energy is used than usual.

An electrolytic plasma polishing machine processes the part in two stages. At the first, the surface is degreased, and at the second, the grinding itself occurs, which, in turn, also consists of two cycles: cutting off the rough layer and grinding the metal. Cleaning from grease is mandatory, since a viscous surface leads to oxidation of the metal and deterioration in the quality of its finish.

If you want your jewelry and accessories to regain their beautiful shine, try some of these simple recipes to clean brass at home. Before testing any of the following recipes, make sure you are dealing with real copper. Take a magnet and touch it to a metal surface - if it sticks, you are most likely holding a copper-plated metal object in your hand. In this case, we advise you not to use acids such as vinegar and soda, but prepare soap solution and use a toothbrush to gently scrub the item.

Classification of metal polishing pastes

You can bring a metal surface to a mirror state with your own hands without the use of machines; just pay attention to special tools, divided into the following groups:

Aquatic. The substance does not contain fat and does its job perfectly;
Organic products - contain paraffin and various oils. They are diluted with various oils and fatty acids;
Diamond paste is a revolutionary solution that allows you to instantly achieve shine on any metal surface.

Let's take a closer look at the last version of grinding. Diamond paste is so effective that it completely replaces a polishing machine. Diamond Substance is available in two types: ASN and ASM brands (expensive).

Rinse and dry well with a cloth. However, if the magnet does not stick, you are dealing with real copper. In this case, you can use one of the other cleaning suggestions. In many cases, you don't need anything more than a little soap and water to clean brass jewelry or accessories. Wipe them well with a sponge or brush, dry them and polish them with jewelry cloth. If you don't have one, a simple household microfiber cloth will also do a great job. Roll the metal in a circular motion and restore its shine.

Diamond paste has the following advantages:

Accuracy. Synthetic diamonds allow you to polish any metal product to a shine as accurately as possible;
Wide range of grain sizes. There are more than 12 grit types available on the market today;
Simple operation allows you to carry out cleaning procedures yourself without the use of special tools;
Diamond paste requires minimal tools: a rag, water and rubber gloves.

The main disadvantage of the cleaning product in question is its high price. On average, diamond paste on the consumables market costs more than 500 rubles per 35 grams of the substance.

Salt is an excellent assistant in environmental cleaning. We've already mentioned salt as a great tool for cleaning brass and other copper items in this article. In a small bowl, combine a couple of tablespoons of salt and 1 tablespoon of water. Mix well until you get a thick paste. Brush the surface of the brass with the mixture, for small curves, corners and details you can use an old toothbrush. Wipe the surface with a cloth soaked in vinegar.

We present several specialized tools, which are necessary in their field of application. This is a surface treatment of various metal products aimed at eliminating impacts and burrs, leveling welds, cleaning rust and old paint coatings, stains from metal oxidation and others. They are used where they are intended for cleaning and grinding metal surfaces to obtain varying degrees of smoothness and be polished to a metallic shine.

Working principle of diamond paste

Diamond paste acts on a metal product mechanically and chemically, forming dispersed films. The composition of the cleaning agent includes substances that promote the occurrence of adsorbing processes, which facilitates grinding of the material.

Diamond paste is applied to different types of fabrics (felt, microfiber or jeans), paper, rubber, plastic and other types of non-metallic materials. It is worth noting that diamond paste can also be applied to polishing wheels to increase the efficiency of metal surface processing. In this way you can achieve a mirror effect. Circles made of felt, felt or leather are installed on the polishing machine.

It also allows you to treat areas where a classic tool cannot reach. Because it works to a degree of polishing, it is most often done on metal surfaces that are left exposed and their special "metal" beauty will not be hidden under the paint finish. In short, it is usually stainless steel. It is obvious that alienation leading to the loss of national identity is not only a typical Bulgarian phenomenon. Stainless steel products are widely used in the chemical industry, for all types of liquid storage containers and piping for the production of medical equipment, the food industry - in general, anywhere important is steel that does not interact or corrode when exposed to chemical aggressive substances.

Description of the polishing process

To grind a metal surface you will need: laps and several tubes of diamond mixture with different grits. Diamond paste is evenly distributed over the working surface of a rag or other material. Experts have noticed an interesting pattern that makes it possible to improve the quality of metal processing.

Besides its practical side, so that stainless steel products are widely used in home cooking, cut and polished to a high-gloss surface imparting exceptional decorative effect, so some of the most luxurious and timeless, bathroom and kitchen cabinets, railings and others. Elements of home and home furniture are made of stainless steel.

This type of steel also has its own mechanical characteristics. They weld well arc welding in an argon environment, which is difficult to deploy with a drill due to their high viscosity. In terms of their surface treatment, another important feature is that they have significantly lower thermal conductivity than conventional steel. Therefore, for example, for a more intense carbohydrate disk, the material can easily overheat and a characteristic blue surface color appears. This requires processing at low disk speed or moderate tape speed.

It turns out that you need to add castor or olive oil to the polishing substance. The ideal ratio is a mixture consisting of 40% diamond dust and 60% oil. After dilution, the mixture is immediately applied to the metal surface.

This, however, should not affect the power of the electric motor or the amount of torque that is transmitted to the grinding wheel or shaft driving the belt. This gives a truly magnificent six, each machine, for processing stainless steel surfaces, with the same success and for the same purpose, except it can be used for processing products made of ordinary steel or non-ferrous metals. It is also important to emphasize that while machines are by far the most important element in this program, they will be useless without a wide range of grinding and polishing discs, sheets, strips, washers, felts, abrasive pastes, wire brushes, etc. this is what Metabo offers them.

Experts recommend starting work only with large grains, gradually moving to abrasives. During processing, make sure that no unnecessary elements - dust, sawdust, hair or pieces of rags - get into the mixture. The presence of foreign objects greatly impairs the polishing to a shine. It is also recommended to wash your hands after changing from one grit to another.

Additionally, flat, concave or convex surfaces, including the outside surface of pipes, can be machined in otherwise inaccessible areas. This is a small and powerful electric motor with a working disk diameter of 125 mm. Also a characteristic feature of this machine is its high torque - 4.2 Nm, whereas in conventional models with the same power it is 3.3 Nm. The characteristic of this angle grinder is also.

A special rotating grille that protects the motor windings from solid metal particles sucked in by the cooling air flow. The protective screen rotates and locks manually without tools. The working disk is fastened with a special nut and without tools.

Types of Diamond Dust

On modern market You can find products not only for polishing metal, but also other materials, for example, wood, glass, stone, etc. They can be classified by color, for example:

Huge range of diamond paste

Yellow packaging indicates that the substance is intended for grinding ceramic materials and glass products. It is worth noting that this dust can also be used for finishing metal;
Blue packaging. This type of product is used for finishing glass. The grinding agent has a fairly wide selection of abrasive elements - from 60 to 10 levels;
The red packaging is suitable exclusively for treating metal surfaces.

As for the packaging itself, diamond paste is sold in compact plastic jars with a volume of 35–45 grams. The average cost of a jar depends on the size and quality of abrasive materials. The finer and higher quality the polishing material, the cheaper the paste costs. The average price is 450–600 rubles.

Highly wear-resistant self-extinguishing brushes with improved dust and greater particle protection. The machine works with various discs and washers for coarse fine polishing, metal brushes, etc. Particularly useful in combination with lamellar discs with refined corundum abrasive grains of different sizes, suitable for coarse and fine medium surface treatment of plain and stainless steel, non-ferrous and light metals, titanium alloys and the like.

At first glance, it is obvious that this is a tool designed to treat very hard-to-reach places, including corners where it is still possible to reach. The elongated narrow sanding arm, around which the endless belt is stretched and moved, causes the machine to be called a "band saw". The arm can rotate 270° to achieve the most comfortable position.

GOI paste

GOI chrome paste is a universal product used for polishing metal and non-metallic surfaces. Although it was invented in the early 1930s, it is still used to polish metals today.

Polishing paste GOI

This grinder is the most unusual and highly specialized tool in the group of six. Its unusual shape is due to its purpose - grinding pipes and other oval-shaped objects. The fixed arm contains the drive shaft and one guide roller. The second belt pulley is located at the end of the movable arm. Under the influence of a strong spring, this shoulder supports the stretched belt. The maximum segment that the tape can wrap is 270°. It can process pipes with a diameter of up to 180 mm.

The GOI product comes in different grain sizes (classified according to the size of the abrasive materials). There are different types of grain size: fine, medium, and coarse. Fine dust is used for polishing soft and non-ferrous metals, coarse grains are used for rough finishing of ferrous metals and steel.

Features of use. Initially, the polishing agent has a solid structure, which can be diluted with a few drops of machine oil. If you need to polish an uneven metal surface with bends, it is recommended to apply the paste diluted on a rag.

It can be changed easily and quickly by hand without tools. It is specially designed for grinding and polishing stainless steel surfaces. Groups of raw nonwoven fabric, used for cleaning, sanding and finishing - to remove scratches, surface stains and oxidation of the metal surface.

Felt for polishing with polishing paste. He specializes in welding and grinding welds located in corners and other hard-to-reach areas, such as creating safety bars on stairs and other areas. In practice, this is an angle grinder with grinding disc, attached to the end of the elongated arm. This design allows the discs to reach places where a conventional sander cannot reach. To avoid leaving traces of corrosive metal on the treated stainless steel surface, the extended arm is made of aluminum alloy, and the metal washers for attaching the working disk are made of stainless steel.

The second polishing method is intended for processing smooth metal surfaces. Its peculiarity is that on wooden block a small amount of abrasive material is applied. Then it is recommended to make methodical movements back and forth along the surface being treated.

Video: Polishing aluminum

The surfaces of metal products are finished not only to give them a beautiful appearance, but also to protect them from rusting, corrosion by acids, alkalis, etc. In one case, it is enough to file the product, in another, it is necessary to bring the surface to a shine by grinding and polishing , in the third - cover with paints and varnishes; all this can be done yourself at home.

Fig. 1. Finishing of metal surfaces: A - sanding; B - grinding with a file; B - grinding of round products; G - polishing with paste.

After processing metals with a file, more or less deep marks from the notch teeth always remain on them. To make the surface cleaner, smoother and even shiny, it is sanded and polished.

METAL GRINDING

At home, metals are polished with emery cloths after carefully treating the surface with a personal file. To make the skin comfortable to hold, it is wrapped around a wooden block (Fig. 1, A) or a wide file; The ends of the skin are held with the thumb and forefinger of both hands. Convex cylindrical surfaces can be sanded by wrapping sandpaper around them.

First, the surface is treated different directions, coarser coarse-grained skins, then finer ones. The final grinding is carried out in one - longitudinal - direction using sandpaper with the finest grain. When grinding, the product must be held motionless.

METAL POLISHING

A mirror-like shine is imparted to metal products by polishing. Without preliminary grinding, only surfaces that have been carefully processed with personal and velvet files can be polished. The file should be rubbed with chalk. The surface is first processed across the strokes on it. When the strokes along and across are the same, the direction is changed by 90° and this is repeated several times. The surface treated in this way, as well as the grinding surface, is polished with special polishing pastes.

The industry produces polishing pastes under the GOI brand. They consist of fine abrasive powders (chromium oxide, iron oxide, etc.), soft plastic substances composed of wax, stearin, kerosene and other materials. GOI pastes come in coarse (dark, almost black), medium (dark green) and fine (light green). First, they polish with a coarse paste, which makes the surface matte, then with a medium and, finally, a fine paste, bringing it to a mirror shine. The paste is applied to a felt swab, cloth or linen cloth and rubbed onto the surface to be polished.

You can make your own polishing pastes. For polishing steel products, the following composition is recommended (in parts by weight):

Stearine - 32

Beeswax - 6

Technical lard - 5

Lead oxide - 3

Chromium oxide - 80

For polishing and glossing brass and nickel-plated surfaces, use pastes of the following composition (in parts by weight):

Stearin - 5

Technical lard - 1

Chromium oxide - 14

The polished surface is wiped with a rag soaked in kerosene, and then dry with a clean rag.

Polishing is the final process of manufacturing a part, carried out using in various ways in order to remove a minimum layer of metal to achieve a mirror-like shine of surfaces. These are interrelated physical, chemical, electrical influences, the choice of which depends on the type of material, the tool used and the characteristics of the external environment. The required quality is achieved by replacing abrasives and methods of exposure. Polishing time depends on the initial quality of the metal.

GOST requirements for metal polishing

Requirements for the quality of metal and coatings are defined in GOST 9.301-86. The surfaces should be free of shells, pores, rust, cracks after grinding, scale, and burrs. To the degree of gloss regulatory requirements No.

At enterprises involved in metal processing, incoming inspection of surfaces is carried out. If necessary, the following is carried out:

processing compressed air containing abrasive (steel shot) (rust and scale are removed);
treatment with metal brushes to remove oxides and etching sludge;
degreasing heated in organic solvents (chlorinated carbons) to remove grease;
degreasing in alkali solutions (removal of mineral oils);
degreasing in electrolyte (electrochemical).

At home, surfaces are wiped with a solvent, processed with a file or grinder with a disk with the appropriate grain size.

Metal polishing class

The polishing class is determined by the surface roughness (the height of the unevenness in microns) of a specific part. The roughness corresponds to the area of use. There are 14 cleanliness classes in total, which are designated in the drawings by an equilateral triangle. Numerical values of roughness after metal polishing are indicated in GOST 2789-59.

Metal polishing class

Surface Appearance	Height of irregularities (up to microdistrict)	Class	Type of processing
Traces of processing are clearly visible			Turning, milling, planing


Traces of processing are almost invisible		fourth	Semi-finishing


Traces of processing are not visible			Fine turning, grinding


Mirror-like surface			Lapping polishing
		eleventh
		twelfth
		thirteenth
		fourteenth

In industry, to measure the height of irregularities, special devices: profilers and microscopes. At home, roughness is determined “by eye”.

Existing methods of metal polishing

The most common methods of polishing metal:

mechanical (abrasive);
chemical (pastes, solutions);
electrochemical (in electrolytes);
ultrasonic.

Mechanical polishing of metal can be dry or wet.

The process can be carried out:

manually;
in semi-automatic mode;
automatically.

Important! With manual processing, you can monitor the process and influence the result. It is impossible to achieve high quality and productivity.

Semi-automatic is special equipment and a qualified specialist. Processing is carried out on metal polishing machines; technological parameters are changed manually. With automatic processing in mass production, human intervention is not required. The work is carried out very quickly and with high precision. The volume of defects is minimized.

Manually polish small parts at home. Apply the paste to a cloth and rub the surface in a circular motion. For surfaces large sizes most often used grinding machines(grinders) or drills equipped with attachments of various grain sizes.

You can install various attachments on the disk. If the nozzle is made of felt or fabric, it is moistened with paste. Professional tools are used in auto repair shops, as they allow you to process fairly large surfaces. Small metal processing plants use machines equipped with polishing belts or felt (cloth) wheels.

Mechanical methods also include abrasive technology for polishing metal in vibrating drums filled with dry abrasive or solution. Rotation and vibration can quickly reduce roughness. If the method is dry, then the solution is replaced with oak or ash sawdust, pieces of felt or suede. If a solution is used, then in addition to polishing steel balls, you can add alkali (for example, a solution of laundry soap) to it, which speeds up the process.

But mechanical polishing has a number of disadvantages:

there is a possibility of the introduction of abrasives into the metal structure;
high costs for installations and resources;
processing consists of several stages;
the process is difficult to manage;
requires significant manual labor and time.

Important! Chemical polishing has higher potential, especially when it comes to elements decorative finishing premises made of various alloys or expensive metals.

When using this method, metal products are immersed in solutions of a certain temperature. When passing chemical reactions the roughness melts within a few minutes. Manual labor Almost no, no power tools or equipment for polishing metal are required. The surface is processed evenly, the configuration of the part does not matter.

But there are also disadvantages. A mirror shine is not achieved (the surface is rather matte), the solution needs to be changed frequently, it is quite aggressive (most often it is an acid). Work can only be carried out in special clothing; the room must be equipped with a high-quality ventilation system.

During electrochemical polishing, parts are also immersed in a solution, but electric current. Since the surface is uneven, the oxide film is thicker in microcavities. The solution processes smooth parts of the surface with a thin layer of oxide faster. At the end of the process, the surface is perfectly smooth. A small investment of time makes it possible to increase productivity.

The disadvantage is high energy consumption. If the surface is rough, mechanical grinding is required. It is necessary to carefully monitor the quality and temperature of the solution, and current density. Solutions are created from acids, so safety regulations must be followed. To reduce costs, it is advisable to pre-process the material mechanically.

Large enterprises are trying to automate and robotize polishing. This can be done using ultrasound, which increases productivity by 30 times and eliminates the need to purchase wheels and pastes. Electricity consumption is lower than when using a chemical or electrochemical method.

Metal Polishes

The technology of manual metal polishing requires the purchase of equipment (drills, grinders) and various attachments.

Basic metal polishing products mechanically– various pastes containing silicon, zirconium or titanium carbide, diamond chips, chromium oxide. Solid pastes must be diluted with oil. The costs are high, since the process consists of several stages, each of which requires different attachments.

If a chemical or electrochemical method is used, large containers and acids are needed for preparing solutions, and special clothing. Nitric, hydrochloric, sulfuric, phosphoric acid, glycerin, and benzyl alcohol are used. For household These are quite expensive purchases, so chemicals used only in enterprises.

Metal polishing machines

All polishing machines are divided into 2 groups: with wheels and belts. Belts and wheels consist of abrasives; the selection takes into account the requirements for surface roughness after processing. The equipment is semi-automatic or automatic. Automatic machines can become part of lines used in mass production.

Any machine is equipped with a bed (platform) that does not change position during operation. An electric motor is mounted on the platform, driving the shaft. You can work with sharpening abrasives and wheels. The sharpening angle is adjusted manually or automatically. Some designs are equipped with a water tank necessary for cooling.

Machines available for processing raw materials (steel sheets, aluminum, brass, profiles) and finished products:

ship fittings;
plumbing equipment;
metal cornices and railings;
door handles, parts of candlesticks;
bicycle parts;
tables and chairs;
mufflers for motorcycles and cars.

Power industrial models 700-950 W, they are connected to a 220 V network. Rotation speed is 90-150 rpm. The adjustment is made depending on the characteristics of the material being processed and the wheel format. At the first stages of processing, large circles are used, small circles are used for finishing. The package includes a cable and extension cord. During work, tools for measuring angles, stabilizers, and pastes may be required.