Etching is a metal treatment process, as a result of which a layer of a certain thickness is removed from the surface under the influence of active chemicals (acids or salts with an acidic reaction), as well as direct current in an electrolyte bath.

Metal pickling can serve a variety of purposes and can be used in industry and at home. The surface of the product subjected to etching acquires a number of technological and decorative properties and allows you to examine its microstructure in a metallographic microscope, remove scale and other non-metallic inclusions from the surface, obtain the necessary jewelry ornament or prepare for soldering.

Etching, also called electrochemical engraving, is most often used at home or in the garage to obtain relief images on various objects with decorative functions. Most often, steels with high hardness are subjected to it, the processing of which with a conventional engraving tool requires a lot of effort. This process is not very difficult even in the absence of artistic skills, if you follow its technology.

Metal surface preparation

In order for the etching process to proceed with high speed, and the thickness of the removed layer was the same, all dirt and traces of oils should be removed from the surface of the product. For this, ordinary detergents and cleaning products used for washing dishes and warm water are suitable. After washing and drying, the surface should be wiped with a fiber soaked in a solvent, which, in addition to degreasing, helps to remove moisture residues.

Separately, it should be said about the quality of surface treatment. Mirror polishing is guaranteed to give a good contrast pattern even at a small etching depth. But if its implementation is impossible for any reason, the surface can be treated with sandpaper so that the risks from it go in one direction. It will also give a good optical effect.

drawing

To apply a pattern to a metal, you can use a lot of different methods that work according to the same mechanism: areas that are not subject to etching are protected from exposure to an aggressive environment or electrolyte.

Method number 1

The most affordable way is to apply ordinary nail polish to the protected areas. However, it has a number of significant disadvantages:

• The viscosity of the varnish does not make it possible to make the lines thin enough to obtain patterns of high complexity;
• Good ability in fine arts is required;
• Correcting inaccurate lines is difficult.

Method number 2

First you need to apply a protective layer on the entire surface of the product. To do this, you can use primers GF-021, XV-062 or bituminous varnish, available in auto parts and household goods stores. After the coating has completely dried, using a gel pen or a thin marker, you can apply the contours of the future image. For this task, you can attract an experienced artist.

Further, from a copper (possibly brass) wire or rod, the diameter of which is selected based on the convenience of holding in the hand, it is necessary to make a needle with a pointed end and scratch the primer along the image lines to the metal. Harder needle material may damage the polished surface of the product.

Already at this stage, it is possible to assess the relief of the future ornament. To obtain areas with different depths of metal etching, for example, contours and penumbra, this process can be carried out in two or more cycles.

Important! In the process, the primer should not chip off. Before drawing a picture, it is worth experimenting and making sure that it is suitable for work.

Method number 3

You will need a laser printer, glossy paper, imaging software, and an iron. The selected image must be formatted (fit to size, made mirrored) and printed. The most affordable source of glossy paper is women's magazines.

The printed image is applied to the surface, covered with a regular landscape sheet on top (to protect the iron) and ironed. After cooling, the paper is washed off under running water, and the toner layer remains on the metal surface.

This method is often used for etching printed circuit boards. Its main drawback is that the pattern is applied only to a straight surface.

Important! Gloss underwater is hard to see. After drying, you need to make sure that it does not remain on the product.

Care must be taken to protect all surfaces of the product. To do this, you can use various substances. You can close the back surface with ordinary plasticine: it is a good dielectric.

Metal etching methods

The choice of a particular method depends on many factors: the chemical activity of the metal, the availability of chemical reagents and safety considerations.

chemical etching

It is carried out in a container with an active substance. For carbon steels, solutions of weak acids can be suitable: citric, acetic. Hydrochloric acid works well. Etching in battery electrolyte, nitric acid and rust converter should be treated very carefully: toxic gaseous substances can be released during the process, so it is better not to work with such reagents in the absence of a fume hood and good ventilation.

One of the safest substances is a saturated solution of ferric chloride. It can be bought in stores selling radio components. The advantages of the solution are its practically unlimited service life (when working with iron alloys) and the staining of the etched surface in an even gray color.

The duration of the process is selected experimentally depending on the concentration of the reagent used and the activity of the metal.

Electrochemical etching

Many stainless and acid-resistant steels, for example, 40X13, 95X18, 08X10H18, 03X12H14M2, do not react to acids, so an electrochemical method is used to pickle them.

For it, you will need a plastic or glass electrolyte bath, wires, terminals and a direct current source. A saturated solution will do as an electrolyte table salt. When choosing a container for it, it should be remembered that the process can proceed quite rapidly, so its volume should be 2 times larger than that of the electrolyte.

Batteries can be used as a current source, but it is better to use a charger (3 - 10A) with an ammeter and the ability to adjust the current parameters to select their optimal value. The workpiece is connected to the anode (positive contact) with the help of terminals and a conductor; any stainless plate placed in the bath parallel to the front surface of the workpiece can be used as a cathode. After that, the device is connected to the network.

The whole process can take from two minutes to half an hour, depending on the current strength and the area of ​​\u200b\u200bthe pattern. The etching depth should be controlled by periodically removing the part from the bath. In this case, do not forget to turn off the power.

At the end of the process, the protective coating can be removed with a suitable solvent and the results of the work evaluated. Due to the good adhesion of the etched surface, it is possible to create a colored pattern.

To do this, the entire surface of the product is blown from a balloon with nitro enamel, and after it dries, it is wiped with a piece of clean leather, felt or other non-abrasive material. The paint is removed from the polished surface, leaving only in the depressions.

Dear readers, if you still have questions, ask them using the form below. We will be glad to communicate with you;)

Etching is a process in which part of the metal is removed from the surface by chemical means. This method is used for the final processing of the part, when preparing the workpiece before applying the coating (galvanic), as well as for creating all kinds of drawings, ornaments and inscriptions.

The essence of the method

Metal etching involves careful surface treatment. A protective coating is applied to the product, which is washed in place of the pattern. Then either acids or an electrolyte bath are used. Unprotected places are destroyed. The longer the exposure time, the deeper the etching of metals occurs. The drawing becomes more expressive and clear. There are various ways to obtain an engraving (inscription): the image itself or the background can be etched directly. Often these processes are combined. Multi-layer etching is also used.

Etching types

Depending on the substance used to destroy the surface of the material, the following etching methods are distinguished.

1. Chemical method (it is also called liquid). In this case, special solutions based on acids are used. Thus, ornaments and inscriptions are applied to the alloys.

2. Electrochemical etching of metal - involves the use of an electrolyte bath. It is filled with a special solution. Lead salts are also often used to prevent overetching. This method has a number of advantages. Firstly, the drawing is clearer, and the time required to complete the process is significantly reduced. In addition, such metal processing is economical: the volume of acid used is much less than with the first method. Another undoubted advantage is the absence of harmful gases (mordant does not contain caustic acids).

3. There is also an ion-plasma method (so-called dry). In this case, the surface is damaged minimally. This method is used in microelectronics.

Steel Pickling

Basically, this treatment is used to remove scale and various oxides. This procedure requires careful adherence to the technology, since overetching of the base metal is undesirable. In the process, both a chemical method and electrolyte baths are used. Hydrochloric and sulfuric acids are used to prepare solutions. All parts require careful degreasing of the surface. Even a small fingerprint can ruin the workpiece. As a protective coating, varnish based on rosin, turpentine, and tar is used. However, it is worth remembering that the components are flammable substances, so the preparation of varnish requires great concentration and caution. After the metal processing is completed, the etching process itself takes place directly. Upon completion, the part must be cleaned of varnish.

Picklings used for steel

Very often, a solution of nitric acid is used to pickle steel. Also used is salt, tartar (with small additions of nitrogen). Hard steel grades are pickled with a mixture of nitric and acetic acids. Glyphogen is a special liquid based on water, nitric acid and alcohol. The surface is treated with this composition for several minutes. Then washed (solution of ethyl alcohol in purified water), dried quickly. This is a pre-treatment. Only after such manipulations are the workpieces placed in the pickling solution. Cast iron is well pickled in a solution of sulfuric acid.

Pickling of non-ferrous metals

Copper and alloys based on it are pickled with sulfuric, hydrochloric, phosphoric or nitric acids. The process is accelerated by solutions of chromates or nitrates. The first stage is the removal of scale, then the brass is directly etched. Aluminum (and its alloys) are etched in a solution of caustic alkali. For casting alloys, nitric and hydrofluoric acids are used. Spot-welded blanks are treated with phosphoric acid. Titanium alloys are also pickled in two stages. First - in caustic alkali, then in a solution of sulfuric, hydrofluoric, nitric acids. Titanium etching is used to remove the oxide film before electroplating. Molybdenum is treated with a solution based on sodium hydroxide and hydrogen peroxide. In addition, etching of metals (such as nickel, tungsten, for example) is carried out using water, hydrogen peroxide and formic acid.

There are several ways to etch boards. In the first case, water and ferric chloride are used. It can also be made independently. To do this, iron filings are dissolved in hydrochloric acid. The mixture is kept for some time. Also, etching of printed circuit boards is carried out using nitric acid. The whole process takes about 10 minutes. At the end of it, the board must be thoroughly wiped with baking soda, as it perfectly neutralizes the remnants of a caustic substance. Another etching composition includes sulfuric acid, water, hydrogen peroxide (in tablets). It takes much more time to etch boards with such a composition: hot water, table salt, blue vitriol. It is worth noting that the temperature of the solution should be at least 40 degrees. Otherwise, etching will take longer. Boards can also be etched using direct current. As dishes for this process, you can use glass, plastic containers (it does not conduct current). Fill the container with edible salt solution. It is he who is the electrolyte. As a cathode, you can take a copper (brass) foil.

Pickling process for other materials

Currently, this type of glass processing, such as etching, is widely used. Vapors of hydrofluoric acid, hydrogen fluoride are used. First, acid polishing of the surface is carried out, then a pattern is applied. After these manipulations, the product is placed in a bath with an etching solution. Then the glass is thoroughly washed and cleaned of the protective coating. As the latter, you can use a mixture based on beeswax, rosin, paraffin. Etching glass with hydrofluoric acid is used to give it a haze. There is also the possibility of color etching. Silver salts give the surface yellow, red, blue hues, copper salts - green, black, red. To obtain a transparent, shiny pattern, sulfuric acid is added to hydrofluoric acid. If deep etching is required, the process is repeated several times.

Pickling Safety

Metal pickling is a rather unsafe activity that requires a lot of concentration. This is due to work with aggressive materials - acids and their mixtures. First of all, for this process it is necessary to correctly choose a room with good ventilation. Ideal when pickling will use a fume hood. If one is not available, then it is necessary to take care of a respirator to avoid inhalation of harmful fumes. When working with acids, rubber gloves and an apron should be worn. Always have baking soda on hand, which - if necessary - can neutralize the effect of the acid. All pickling solutions must be stored in special containers (glass or plastic). Do not forget about the stickers, which will indicate the composition of the mixture, the date of preparation. There is one more rule: jars of acids should not be placed on high shelves. Their fall from a height is fraught with serious consequences. Artistic metal etching is not complete without the use of nitric acid, which is quite caustic. In addition, in some mixtures it can be explosive. Most often, nitric acid is used for sterling silver. Etching solutions are prepared by mixing acids with water. It is also worth remembering that in all cases the acid is added to the water, and not vice versa.

Hello dear readers! Today, in this article, the author of the video will tell us about how you can apply any image on metal at home in a fairly simple way.

To get started, I suggest watching this homemade video, which is presented below (it consists of two parts):

So, as you already understood, today the author will tell us how you can easily apply any image to any metal that can no longer be removed in any way. We will apply the image to the metal by etching. This method is similar to the engraving method, but it does not require any nozzles or drills.

So, let's begin.

For ours, we need the following components:
- the metal on which we will apply the image (in our case, this is a knife);
- Scotch;
- self-adhesive wallpaper or glossy paper;
- plasticine;
- cotton pads;
- saline solution (you can make it yourself very simply: mix one tablespoon of salt in half a glass of warm water);
- wires with "crocodiles";
- power supply or battery from 8 to 12 volts;
- one sheet of A4 paper;
- iron;
- laser printer.

Let's get to work.
First, take the self-adhesive paper and carefully peel it off the glossy paper:

Now you need to carefully stick with tape or in our case "self-adhesive" this glossy paper on an A4 sheet like this:

Now in the computer we select the image that you want to see on the metal and if there is an inscription there, then it should be done in a mirror image. We print the image on a glossy sheet:

Next, with the help of scissors, you need to carefully cut out our drawing, without touching the image itself, so as not to blur or erase it:

Now we apply our stencil to the knife and try to do everything the first time (so that you don’t have to move the stencil), since the image will be streaked:

Now you need to take the iron, after setting it to the second mode, and very carefully iron our stencil for one minute:

Now, while our knife is still hot, we take cotton pads and gently stroke the stencil, thereby "pressing" the paint into the metal:

After the knife has cooled down, you can peel off the paper (do this slowly and very carefully):

As a result, you should get something like this:

Now you need to take the adhesive tape and paste the knife around the image, so that the saline solution does not get on the entire surface of the knife and the etching is neat:

Now we cover the image with plasticine to get such a "bath" that will not let the saline solution through:

Pour saline solution into our "bath" (about three teaspoons):

Next, let's move on to the wires ... we hook the "plus" of the battery to the knife:

We connect the second "crocodile" to the "minus" of the battery and now we only need to touch the saline solution:

So let's get started. the saline solution will begin to boil and blacken - this means that an etching reaction is underway. You should keep the wire in the saline solution for no more than 30 seconds, because in the case of prolonged etching, the image will not be clear enough:

Next, you need to disconnect the wires, pour out the black liquid from the "bath" and remove the "bath" itself along with the adhesive tape:

Metal engraving! Basic principles.

The method is based on the method of electrochemical etching of metals. Briefly, it is as follows: The part on which the inscription is made, the drawing (previously applied with a special varnish), is immersed in an electrolyte solution, it is the anode. That is, a (+) current source is connected to it. The cathode, which is also immersed in the electrolyte solution, is a strip of stainless steel. A (-) current source is connected to it. When the current is turned on, electrochemical etching occurs, that is, the dissolution of the surfaces of the part that are not protected by varnish.

The figure schematically shows the principle of the process.

The numbers show:
1. Metal detail.
2. Etched area.
3. A layer of lacquer keeps the metal unetched.

That is the basis. Now let's look at the whole process in detail.

1. Preparation of the part.

As a rule, it comes down to a thorough degreasing of the surfaces on which the varnish will be applied. What is it for? Firstly, the lacquer adheres very firmly to the degreased surface, which ensures that during the etching process it will not be torn off by parts that will lead to irreparable defects in the form of undesirably etched areas. So you can completely ruin the product.

Secondly: if there is not a degreased area on the surface to be etched. For example, even your own fingerprint! This grease can act as a layer of varnish, protecting the surface from etching. And then you get an etched fingerprint. This defect is unpleasant, but in most cases can be eliminated by re-weeding.

And so we will clean the surface of extraneous dirt, debris, etc. Be sure to wear rubber gloves so as not to leave fingerprints. And it's easier to work in hot water.

Photo: washing the knife under running water with soap.

Degrease by soaking the part in a solution of soap, washing powder in hot water for a while. Then you need to carefully clean the part with a brush (toothbrush is suitable) in the same solution. Pay special attention to blind (not through) holes. They are very hard to wash. You can't leave dirt there. Rinsing is carried out under running water as thoroughly as possible. Don't take off your gloves! Further from this point on, it is generally extremely undesirable to touch the part with hands without gloves, in order to avoid the appearance of the above-described defects. If, nevertheless, you have touched the part, it is better to repeat the degreasing process. How to check the quality of degreasing? Very simple. From a well-skimmed metal, water drains completely, leaving no drops or streaks. If drops remain, water sticks to the metal (exact expression), then there is fat in these places. Scrub them with the solution brush more thoroughly and repeat rinsing and checking.

Another secret. An ultrasonic bath is used to degrease complex parts that are difficult to clean holes, crevices, etc. At home, successfully replaced by a household ultrasonic compact machine. The use of ultrasound significantly reduces the degreasing time and improves the quality. But in most cases this is not necessary.

Small parts can be degreased by wiping with cotton wool and toothpowder moistened with alcohol. The powder contains soda, which will remove fat. A very fast way to degrease, but requires a certain skill.

Photo: degreasing with alcohol and tooth powder.

2. Preparation of a special varnish.

For drawing inscriptions and drawings on metal, a special varnish is used. The composition and method of preparation has been worked out as a result practical work and when these recommendations are followed, it guarantees the quality of work. The varnish provides reliable protection of parts from etching and is easily removed at the end of the process. We need the following ingredients to prepare it:

- Tar. The substance is black, fragile. It is widely used in construction for the purpose of waterproofing roofs, during road repairs. Sold in building materials stores in large pieces of 50 kg. For our purposes, this amount is not needed. Therefore, it is easier to look for a piece of tar at construction sites, ask workers pouring roofing or repairing roads. In such cases, as a rule, fragments remain, which are simply thrown away. It is important to find a clean, free of sand and other debris sample. The content of foreign impurities is highly undesirable and will significantly reduce the quality of the finished varnish. main component. The required amount is almost equal to the volume of the finished varnish.

- Rosin. Fragile amber substance. Made from pine resin. Widely used in soldering electrical products. Inexpensive. Sold in hardware stores, can also be sold as part of soldering kits, together with a soldering iron and tin. The required amount is in a crushed matchbox (about 30 cc). About.

- Gum turpentine. Flammable liquid, used as a solvent for some paints and varnishes. Sold in economic departments next to paint. Usually in bottles of 0.5 liters. One bottle is enough.

As you can see, all three substances are readily available and inexpensive. Also not hazardous to health.

The tar must be crushed (split with a hammer) and placed in a metal dish with a lid, in which we will prepare the varnish. Add turpentine there and stir to dissolve. You can leave for a while to dissolve the pieces of tar. Rosin is also crushed and mixed with pieces of tar. Although some sources recommend adding rosin to the already dissolved tar. The main thing here is to ensure melting and uniform mixing. It is desirable to obtain the viscosity of liquid sour cream. Now you need to heat the mixture for better mixing.

Heating is carried out on an electric stove, in a low heating mode. It is not recommended to use heating on a gas burner due to the risk of fire. I single out the most important issue of fire safety separately.

Attention! The varnish and its components are flammable!

Do not use open flames to heat the varnish and do not boil the varnish near the fire! Vapors from molten tar are also flammable! If over the melted varnish appeared grayish white smoke, this is a signal of dangerous overheating. Do not open the lid! Vapors can flare up at any second even from simple stirring. Immediately and carefully, without jerking, remove the utensil with varnish from the heated stove and let it cool. Do not boil varnish in living quarters, it is better to do it in well-ventilated places, as a characteristic smell appears. Just in case, prepare a piece of thick cloth. If the varnish breaks out, don't panic! Do not extinguish it with water! Cover the dish with a tight lid or close the fire with a thick cloth. The flame will immediately go out without access to oxygen. When extinguishing with water, you can be scalded with water vapor, burning splashes of varnish will fall on the body, clothes and objects, and then burns and a fire in the room are inevitable! Never move away from boiling varnish.

The main reason for all the fires is that they forgot the varnish on the tiles and went to drink tea!

If you take reasonable precautions, you will avoid fire. There are practically no cases of fires at work in our time.

Heating with stirring is carried out to a temperature of 60-70 degrees. At the same time, the components are guaranteed to be mixed and a varnish with the necessary properties is obtained. Now the varnish can be cooled and poured into a container with a tight lid for storage. The varnish will thicken a little as it cools.

Simplified varnish preparation.
It is necessary to purchase ready-made bituminous varnish. It is also freely sold in the paint and thinner departments. It is used in everyday life to protect water pipes from rust. The varnish is diluted with turpentine and finely chopped rosin is added. Approximately a matchbox of rosin for 0.5 liters of varnish. Stir thoroughly with low heat until completely dissolved. Don't forget about fire safety! Cool and pour into a storage container.

Before direct use, the varnish is diluted with turpentine to the required density. The varnish does not deteriorate during storage for a long time. If it thickens, you can always dilute it with turpentine.

3. Drawing a picture on a knife (another part).

You will say that only an experienced artist can draw a picture or an inscription. But what about someone who does not have the ability of an artist? Here the situation is not at all hopeless. Even experienced artists resort to simple tricks to significantly improve the quality and speed of drawing. Using this technique, almost anyone (as long as their hands are not shaking, of course!) can successfully achieve good quality. And a little practical experience will greatly give confidence in the work.

First you need to decide on a future miniature or inscription. Make a pencil preliminary drawing at a scale of 1:1 (it's called a sketch). At the same time, no one forbids you to cut out a suitable picture from a magazine, newspaper, etc. with scissors. You can also run it on a computer, who is familiar with the necessary programs, set the required scale and print.

Photo: Preparing a sketch on a computer.

Now let's draw a pattern on the skimmed surface of the knife, details using transfer paper! You just need to use a color translation of yellow, red, white (there is one). Translating black and purple colors does not leave marks on the metal.

Photo: The knife is inscribed with yellow transfer paper.
Horizontal lines are also marked for writing even letters.

Advice from an experienced craftsman: To prevent the drawing from shifting when copied, it and the transfer paper are fixed with pieces of adhesive tape. Then the drawing is translated with a pencil, pen. Prints of lines from the transfer paper will allow you to easily and accurately continue working with varnish.

4. Varnish drawing.

To draw the future drawing, the inscription with prepared varnish, you need to use thin brushes or feathers. Having chosen the optimal thickness of the varnish and with a little practice, you can quickly learn how to draw the translated drawing. With some experience, it is also possible to freely write with a pen, even without preliminary marking with transfer paper.

Photo: the artist strokes the translated inscription with varnish using a brush. Please note: a wooden hand rest is used. Stand in the form of a bench 3 cm high above the table surface. (width 6 cm, length 30 cm). Facilitates precision work and relieves stress, allowing you to work for a long time without fatigue. The support excludes a touch by a hand the degreased surface of metal.

The operation requires some skill and patience. Don't despair if it doesn't work the first time. You can always easily wash off the varnish with the same turpentine, thinner, gasoline (only use pure unleaded gasoline for "nefras" or "kalosha" lighters, leaded gasoline is poisonous!) And try again.

Photo: Binocular glasses with 5X magnification.

Photo: The pattern on the knife is painted with varnish. Please note: solid varnishing of places that are not subject to etching is not completely completed. This is done with the expectation of subsequent surface protection with plasticine!

5. Pre-drying the varnish.

The next technological operation is the preliminary drying of the varnish to a semi-solid state. To do this, it is enough to leave the item in a ventilated place for 2-3 hours at room temperature. There will be a partial drying of the varnish and its thickening.

6. Final study of the drawing.

During the drawing with a brush or pen, you may have made some inaccuracies, mistakes and painted over those places that should have been left under the grass. Now you can fix all these defects. With a sharpened stick made of wood, plexiglass, textolite or a thin metal needle, it is necessary to remove the varnish from overpainted areas. You also need to clean up the edges of the curved lines, making them more even and attractive. Trimming the borders of the lines is also important, since the varnish layer at the edge of the pattern is always thinner, and there is a possibility of undesirable etching. By removing the varnish from the borders of the lines, we thereby make the boundary layer of the varnish thicker and increase its reliability.

Photo: tools for the final study of the drawing. Plexiglas stick, needle at the end of the stick from an old brush, fountain pen.

At the final study, the engraving operation is also performed. It consists in scratching thin lines with a sharp needle attached to the end of a stick from an old brush. So you can make very thin etched lines or write an inscription, imitate the knife number.

Removing grains of excess varnish should be done by blowing off or using cotton wool soaked in alcohol. Alcohol does not dissolve varnish and easily removes debris. If you use turpentine, pure gasoline (galosh) or any other solvent, the pattern will simply wash off completely. This way you can delete unsuccessful work results, which is very possible at the initial stage.

Photo: Fine lines scratched with a needle are very clearly visible.
For this operation, it is desirable to use a magnifying glass, binocular glasses.

7. Drying varnish.

There are various ways to dry the varnish completely. Drying is a very important and responsible operation, the quality of which determines the result of the work.

The most common and reliable way This is oven drying. Temperature 100-130 degrees. Drying time - 30-40 min. Then cooling at room temperature. However, this method is used for large volumes of work. At home, drying in an old electric oven set to the lowest heat setting can be recommended. Do not use ovens that are used for cooking! The remaining smell will remain for a long time and make cooking impossible! If, due to forgetfulness, the drying time is exceeded, there may be cases of overdrying of the varnish.

Another way is natural drying. Just leave the part at room temperature in a ventilated place. Usually in 3-4 days the varnish dries completely. Drying quality is good enough, but very long. To speed up the process, desktop heat-fans are used, with the help of which drying takes place in 1-2 hours.

Photo: Drying varnish with a fan heater.
1 - fan heater.
2 - Details.

After that, the cold air flow mode is turned on and the part quickly cools down to room temperature. Perhaps this the only way drying for parts with elements that are afraid of heating. For example, making an inscription on a knife that has a handle already assembled. You can’t heat such a knife in a drying cabinet, you can just burn the handle!

A special warning applies to knives where the handle is bonded to the blade with epoxy resin. When heated to 80-90 degrees, the resin softens and collapses. When it cools down, it will not harden again. With such a knife you can work only after disassembly. How to remove the handle? Very simple: heat the blade to 80-90 degrees, and pull out the handle!

With natural drying, there is practically no danger of overdrying the varnish.

A high-speed drying method is possible when using an electric stove. The part is held with the help of a heat-insulating device (you can use pliers) above the heated surface of the electric stove at 5-10 cm. The method is quite dangerous in overheating the varnish and igniting it. The end of heating is considered the moment when the temperature reaches 100-130 degrees. At this temperature, a drop of water that has fallen on a heated part hisses and rolls on the surface. What can serve as the simplest indicator of heating. Then cooling to room temperature follows. If you overheat the part, you can very easily dry out the varnish.

Qualitatively dried varnish acquires rigidity and when pressed with the tip of the nail, no dent remains.

8. Danger of varnish overdrying.

When overheated or too long drying, the varnish becomes excessively durable to such an extent that it becomes impossible to remove it with gasoline or any other solvent! Such a varnish turns into a durable coating, which can only be removed mechanically: by grinding with sandpaper or even on sandpaper!

So you can very easily spoil the part or knife. Don't forget about the part in the drying cabinet or above the tiles! Better set a timer for a reminder!

Forgetfulness is the main cause of overdrying and fires!

Don't forget about fire safety rules! All the above precautions remain relevant during this operation!

Carefully inspect the quality of the dried varnish. It is very possible for bubbles to form during very rapid heating. They need to be tinted and dried for an additional short time.

Photo: detail after etching, bubbles that appeared during drying led to the appearance of undesirably etched points (highlighted in red). The defect is irreparable.

9. Operation after drying.

Before subsequent weed, it is necessary to additionally rinse and degrease the part, which is done by lightly rubbing with cotton wool moistened with alcohol and a small amount of ordinary tooth powder. Then finally with pure alcohol. We have already discussed the need for this in the chapter on surface degreasing. You will also additionally check the strength of the dried varnish.

10. Preparing the part for etching.

It is not at all necessary to paint over all other surfaces with the same varnish. It is enough to confine ourselves to the zone near the inscription, drawing. Plasticine, polyethylene and other improvised materials can be successfully used for protection. Plastic lids and packaging from mayonnaise and other products can be very useful, from which it is convenient to cut out the necessary templates. You need to carefully wrap the handle of the knife with plastic wrap, securing it with electrical tape and tape. Plasticine, ordinary, for children, will reliably protect metal surfaces from etching. In general, it is necessary to try, if possible, to protect large painted surfaces with an additional layer of plasticine, which will provide additional protection against unwanted mordants. Running a little ahead, we note that it is immediately necessary to take care of fixing the electrode, the place of fixing must also be protected. At this stage, there can be no specific recommendations, it all depends on your capabilities and the properties of a particular part. The main requirement is to ensure hermetic protection of parts that are not subject to etching.

Photo: the knife is prepared for etching the inscription. The handle is protected by a layer of polyethylene and adhesive tape. The blade is protected with plasticine. Only the etched inscription is left open.

Photo: detail prepared for etching. Protection with plasticine. The wire for connecting the current is clearly visible.

11. Installation for etching.

The general device of the installation can be considered in detail in the diagram. It consists of a direct current source, an etching vessel (bath) with an electrolyte, stainless steel electrodes (cathodes), a part to be etched, and conductors connecting the current source to the electrodes.

Let's explain in more detail.

DC source.

In general, the source must provide a constant current of 3-10 amperes, an ammeter is required that constantly shows the current. It is desirable to have inadvertent short circuit protection, which is successfully provided by a fuse of the appropriate rating. In practice, there is no need to purchase an expensive current source with a digital indication and a built-in timer. An excellent solution is a device for charging car batteries. It is very possible that it has been in your garage for a long time. Yes, and buy cheap. As a rule, such devices are equipped with an ammeter, a fuse and a current switch. For craftsmen familiar with electrical circuits, it is recommended to assemble a homemade rectifier. I note that smoothing capacitors at the output of the current source are not at all necessary, a rectified current with the presence of ripples is quite suitable. For pulsed current sources, a capacitor is still necessary.

Pickling bath.

It is desirable that the bath be made of a non-conductive material. For example: polyethylene, plastics, etc. The main requirement: the part must be freely placed in the bath, completely immersed in the electrolyte. It is possible to carry out weed in metal dishes, but it is necessary to isolate both the electrodes (cathodes) and the part from electrical contact with each other. Remember that this greatly increases the risk of electric shock! Do not touch the metal bath when the current is on! Such a bath must be grounded. The safest way is still to use non-metal utensils. Get creative. For example, for weeding long blades of swords, sabers, checkers, a cut of a polyethylene pipe with a diameter of 150-200 mm and the required length is used as a bath. From the bottom of the pipe, of course, it is muffled by a lid. Often, it is quite possible to adapt a plastic bottle from mineral water, 1.5 or 2 liters of beer for weeding a single copy of a knife, having previously cut off the upper part. Although the electrolyte is harmless enough, it is still not recommended to use food utensils for pickling.

The composition of the electrolyte.

A simple salt solution is suitable for weeding most modern stainless steels! For a liter of plain (not distillate) hot water, 3-5 tablespoons of salt and mix thoroughly. Sometimes it is recommended to add 8-10 milliliters of hydrochloric acid (concentrated) to such an electrolyte. Take extreme care when handling acid! Although in practice, weed goes well without it.

To pickle rusting grades of steel, copper, brass, aluminum, a tablespoon of copper sulfate is added to the salt solution. It is sold in the household departments, fertilizers (bluish-green powder). I note that aluminum will be etched without current being connected at all, with the release of a large amount of heat. The electrolyte may boil.

The electrolyte is relatively harmless to health, you can work without gloves, but there will be stains that are difficult to wash off. After work, you should still wash your hands with soap and warm water. It is entirely possible to flush the used electrolyte into the city sewer, along with plenty of water. The electrolyte has a limited service life. That is, in the process of etching, it is saturated with metal salts and gradually loses its properties. Insoluble precipitates of brown and green color also accumulate and pollute the pattern, making it difficult to observe the process. This electrolyte needs to be replaced. Or let stand and carefully pour, discarding the sediment.

Previously, solutions of strong acids were used for etching without the use of electric current. We do not recommend doing this. This is a rather dangerous and unhealthy process that requires exhaust ventilation; it is necessary to work in glasses with the use of protective equipment. In addition, modern steels are so resistant to acids that it will take a long time without a guarantee of results.

And our simple safe electrolyte copes with any steel!

Electrodes (cathodes, -).

The most suitable material for manufacturing is mild stainless steel. It is used to make dishes, thermoses, water tanks, spoons, forks. Most often, the electrodes are strips sheet steel located on both sides along the walls of the pickling bath. If the part has an etched pattern on one side, it is necessary to place the electrode opposite the surface to be etched, otherwise etching with different (uneven) depths is possible, which is a noticeable defect. Accordingly, if we poison two opposite sides of the part (knife) at once, the electrodes should be on two opposite sides. The size of the electrodes (their surface area) is not particularly critical. Most importantly, the electrode must exceed the etched area, otherwise it is possible to obtain an uneven etching depth. To etch a small inscription on a knife, the author successfully used an old stainless steel tablespoon. (True, then it had to be cleaned with an emery cloth for a long time!) The service life of the cathodes is not limited. They do not dissolve during operation, but only become contaminated. Metal salts are deposited on them; when brass is etched, a layer of copper is deposited on them.

Photo: brass etching. After 15 min from the beginning of the process, a copper layer appeared on the electrode, which can be easily removed by washing in hot water. Then the etching continued.

Care for them consists in rinsing with hot water and sanding a little. The cathode plates must necessarily have holes to which the terminals for connecting conductors are attached. A simple and reliable way is to clamp the wire with a screw with a nut and washers. Ensure reliable contact! Weak contact causes heating, sparking and the electrode can turn off without you noticing! And then you will wonder why one side of the part was etched well, and the other very weakly.

Conductors.

There are two requirements: they must withstand current up to 10 amperes without heating and have waterproof insulation.

Pickling room
(Click on the picture to enlarge it)

Hidden camera photo: Etching room at the plant.
1 - Current sources.
2 - Stainless steel pickling bath.
3 - Plasticine.
4 - Brass pickling bath - small. It is made of a polyethylene tank of 50 liters. Covered with polyethylene.
5 - Bath for pickling brass - large.
6 - Exhaust ventilation. Used in acid etching. Currently not working.

12. Etching process.

We assemble the installation according to the scheme. We pay special attention to the correct observance of polarity. Rigidly fix the part and electrodes in the bath. Let's check if there is a short circuit between them. The current strength for etching a pattern on one medium-sized knife is about 3 amperes. It is necessary to set the battery charger to the minimum current value. Increasing the current will result in faster etching, but is still not recommended due to the possible phenomenon of lacquer stripping. Monitor the process constantly. The appearance of pieces of lacquer on the surface of the electrolyte indicates a possible partial separation of the lacquer. It is necessary to stop the process, remove the part, rinse gently under a layer of water and carefully examine. The places where the varnish has been torn off must be tinted again and dried again. Then continue the process. If you will etch a drawing or an inscription of large sizes, you need to increase the current strength accordingly. The etching time is 30-60 minutes. In an average of 45 minutes, a sufficient depth of etching can be achieved. Control the depth visually, from time to time taking out the part. To apply a knife number or a thin inscription, a small depth and time of 15-20 minutes are enough. Over time, you will gain experience and be able to determine with sufficient accuracy when you need to complete the etching.

Photo: etching in a glass jar.
The electrode and the workpiece are fixed with clothespins. The electrode is located only on one side, which is not entirely correct. However, the process went remarkably well.

13. Wash.

Disconnect the etched part from the electrodes (after turning off the current!), Plasticine and other protective equipment are removed. The varnish is washed off with a cloth soaked in turpentine. The final, final flush is done with galosh gasoline (for lighters).

The resulting drawing, the inscription have a gray-matte background. It should be noted that against the background of the picture there are metal salts and other indelible substances, etching products. They are not harmful to health and with such a knife you can cut food. For most purposes, the work can be considered finished.

Photo: Finished drawing on the knife. Etching time 30 minutes. Current strength 2.5 Amps. There are no defects.

Photo: Brass detail. Etching completed.

Photo: Same detail. Plasticine removed, varnish washed off with turpentine. The depth of etching is clearly visible. Etching time 45 min. Current strength 1.2 Amps. The process was successfully completed in a glass jar!

14. Additional operation for processing the background surface of the picture.

With a little work, you can give the background of the picture a metallic sheen by clearing it of weed products.

Photo: A polished pattern has a shiny background and looks more attractive.

This is done by polishing the pattern, and the rest of the knife does not interfere with bringing it to good condition. Why do we need the following materials:

1. Electric emery or an electric drill with a table attachment device.
2. Pile circle with synthetic pile.
3. Diamond polishing paste. The grain size is 10-40 microns or 7-10 microns. Correspond gray, blue and green colors of pastes. Diamond pastes have colors that match the grain size. You can use pastes with fine grains of 2-3 microns (yellow), it will give a very good shine, but you will have to work longer.

Photo: Polishing the pattern with diamond paste with a grain of 7-10 microns (green). Homemade emery is made on the basis of an engine from a washing machine.

As you may have guessed, it is necessary to fix the circle on an emery board or a drill and carefully polish the pattern using diamond paste. The operation is so simple that it does not require detailed description. It is only necessary to remind that it is necessary to work in goggles and gloves. Hold on tight to the knife! There is a great danger of cutting yourself, especially if it is well sharpened! From time to time wipe the surface with a cloth soaked in gasoline. Quite quickly, the background, as well as other surfaces, will acquire a metallic sheen.

Photo: finishing with a 2-3 µm diamond paste (corresponds to yellow). Please note: a soft cloth circle is used.

In conclusion, it can be noted that small inscriptions can be polished without the use of emery, etc. An old toothbrush will successfully replace the polishing wheel. However, it will take much more time for such cleaning.

Photo: polishing the picture with an old toothbrush.

15. Conclusion.

In this guide, we have considered only the most important, key points of the method. In each case, there may be deviations depending on the tasks and your capabilities. Don't be afraid to improvise and experiment! (Of course not on the things of the customer). It is safe to say that a little practice will give you confidence and allow you to achieve excellent results.

Photo: Examples of successfully completed work.

Each buyer of this technology has the right to ask questions that may have arisen while reading the material to the author of the book.

You can also count on my tips when practical application this methodology.
Questions, wishes and complaints should be sent to mail to [email protected].
I'll try to answer as quickly as possible.

Removing part of the surface layer metal product through a chemical reaction is called etching. This technology has been known to man for several millennia, along with chasing and blackening, it was used to finish metal parts of weapons and household utensils, jewelry and ritual items. Nowadays, metal etching is used in art crafts, for electroplating, for creating images and inscriptions on metal products.

The essence of the method

Before etching, on those parts of the metal surface that should not be etched, a protective coating is applied that is resistant to the etching substance (mordant).

Next, the part is exposed to an acidic environment or immersed in a container with an electrolytic liquid. The longer the part is processed, the greater the layer of metal is corroded by the aggressive environment. Metal etching can be carried out in several stages, this is the so-called multilayer etching.

Etching of images on metal is carried out both in industrial and at home conditions.

Metal etching methods

Based on the materials used to corrode the metal layer, there are such methods of etching metals as:

• Chemical (liquid). Acid solutions are used. It does not require complex equipment and expensive materials. Vapors that are harmful to health are produced during operation.
• Electrochemical. An electrolyte solution is used and passed through it electricity. It is characterized by a higher speed of the process, more accurate execution of the details of the pattern, economical consumption of the working fluid. Does not produce harmful fumes
• Ion-plasma (dry). The surface layer is evaporated by an ionized plasma beam. Used in the production of microelectronic components.

The ion-plasma method requires high-precision and expensive equipment and is used only in industrial production. Liquid method, electrochemical metal etching and even electrochemical engraving are available at home.

With the help of galvanic etching, you can independently make a printed circuit board that is almost as good as an industrial one.

Metal galvanic etching

The galvanic etching method compares favorably with the liquid etching method because it does not require the use of acids that produce harmful fumes. Depending on the workpiece material, different electrolytic solutions are used:

• Steel and iron - ammonia and iron sulfate
• Copper and its alloys (bronze, brass) - copper sulfate
• Zinc - zinc sulfate.

To carry out the process at home, you will need:

• Electroplating bath made of non-conductive material.
• Power supply for 5 volts DC.
• Metal cathode (from the same metal as the workpiece.)
• Wire hangers for workpiece and cathode. The workpiece should not touch the walls or bottom of the tub.
• Two conductive rods longer than the tub.

One rod is connected to the negative terminal of the power supply and the cathode is hung on it.

The other rod is connected to the positive terminal and a product is hung on it, which will serve as the anode.

When voltage is applied, the process of electrolytic transfer of metal from the product to the cathode begins. It will occur from areas of the surface that are not covered with a protective varnish.

Artistic metal etching

Artistic etching of metal is carried out both by galvanic and liquid methods.

Masters of folk crafts and just home craftsmen receive with its help highly artistic images on cold steel and firearms, all kinds of forged and cast utensils. For craftsmen who make author's hunting and household knives, etching has become an almost indispensable element of decoration. Hunting scenes, Arabic, runic or abstract geometric ornaments are especially popular. Many craftsmen combine metal etching with bluing, giving the pattern a bluish, black or yellowish tint.

To transfer images, both the method of coating the part with varnish and glossy paper are used. Another method is also used - gluing the part with tape. The lines of the pattern are scratched with a hot needle, after which the adhesive tape is carefully removed from the areas to be etched with tweezers. The remains of the adhesive mass must be washed off with a solvent.

Before pickling, the part must be thoroughly degreased.

Metal surface preparation

Before etching, the surface must be prepared. This will ensure:

• High process speed
• removal of metal in an even layer.

During surface treatment, all mechanical and chemical contaminants are removed from it. A warm soapy solution is used for it, and any detergent. After the surface has dried, it must be wiped with a rag soaked in a solvent or degreaser. This will remove residual liquid and oil films.

Chemical processing is well combined with mechanical:

• mirror polishing
• sanding. Used when polishing is not available. It should be ensured that the skin moves in the same direction all the time and the traces of it are strictly parallel.

Machining will greatly improve appearance products after etching.

drawing

There are several methods for this operation. All of them are united by a common principle: protecting part of the surface from the corrosive action of the mordant, and distinguishes between the substance used to apply the pattern.

Nail polish

Popular and affordable way. Has some disadvantages:

• The high viscosity of the varnish makes it impossible to draw fine details and fine lines.
• Requires a steady hand and skill in drawing.
• It is very difficult to correct erroneously applied details.

Primer or bituminous varnish

The primer GF 021, XV 062 or bituminous varnish is used. First, the entire etched product is covered with the substance. Next, with a thin pen or marker, the contours of the drawing are transferred. From a thin wire or soft alloy rod, a needle should be made by sharpening the end of the wire.

Those areas of the image that should be etched are scratched to the metal. Care must be taken to ensure that the primer does not chip off.

Glossy paper

In addition to glossy paper (you can buy it at art supply stores, or you can simply cut out a sheet from a magazine), you will need a laser printer, an imaging application, and an iron. The image of the picture should be mirrored and printed in full size. The image is applied to the surface and ironed several times. After the workpiece has cooled, the paper is washed off with warm water, and the toner remains on the surface of the part. The back and side surfaces that are not subject to etching must be protected with varnish or plasticine.

The main advantage of the method is that you can accurately transfer the smallest details of the image.

The main disadvantage is that you can only work with flat or cylindrical workpieces in this way. The method is very popular in the manufacture of printed circuit boards.

Steel Pickling

In addition to artistic metal etching, which allows obtaining exquisite images on steel surfaces, steel etching is also used to remove scale and oxide films. At the same time, special care must be taken to comply with the requirements technological process in everything related to the concentration of pickling solutions and the exposure time of the part in the pickle or in the electrolyte bath. Overetching during such an operation is highly undesirable.

When pickling steel, both liquid and electrochemical methods are used. Pickling is prepared on the basis of strong acids, such as hydrochloric or sulfuric. Particular attention should be paid to thorough degreasing of the surface. A missed oil or grease stain can render the workpiece unusable. To protect parts of the workpiece that are not subject to etching, I use varnishes based on rosin, turpentine, and tar.

These components are highly flammable, so when working with varnish, you should be especially careful and careful. At the end of etching, the unetched parts of the workpiece are cleaned of the protective varnish with a solvent.

Picklings used for steel

Nitric acid is very popular among home craftsmen - picklers. It is used as the only basis for pickling, and mixed with tartar or salt. A metal pickling solution based on a mixture of nitric and hydrochloric acid is very reactive and must be handled with extreme care.

For the treatment of hard and special steel grades, mixtures of nitric and acetic acid are used. The processing is carried out in two stages. First, a special pre-mordant is prepared - glyphogen, which is a mixture of water, nitric acid and ethyl alcohol. In it, the part is kept for several minutes. Next, the workpiece is washed with a solution of ethyl alcohol in distilled water and dried thoroughly. After that, the main etching is carried out.

Sulfuric acid solutions of medium concentrations are used for pickling cast irons.

Pickling of non-ferrous metals

Based on their atomic weight and the physicochemical properties of the substance determined by it, for each metal and alloy they select their own mordant that best affects it.

Both pure copper and copper alloys are pickled using sulfuric, hydrochloric, phosphoric, and nitric acid. Chromium or nitrogen compounds are added to the solutions to increase the reaction rate. At the first stage of etching, scale and oxide film are removed from the workpiece, then proceed to the actual etching of the metal. Care must be taken when pickling copper at home.

Aluminum and alloys based on it are distinguished from other metals by the fact that not acidic, but alkaline solutions are used for their etching. For molybdenum, alkaline solutions based on caustic soda and hydrogen peroxide are also used.

Titanium stands even more apart - at the first stage of preliminary pickling, alkali is used, and at the main stage, acid is already used. For titanium, I use the strongest acids - hydrofluoric and concentrated sulfuric and nitric. Titanium blanks are pickled to remove the surface layer of oxides immediately before being electroplated.

To pickle metals such as nickel or tungsten, an aqueous solution of hydrogen peroxide and formic acid is used.

PCB etching

The blank for the printed circuit board is a textolite sheet, coated on one or both sides with a layer of copper foil. The purpose of etching printed circuit boards is to create conductive traces of copper foil exactly according to the drawing. The tracks are covered with a protective varnish, the rest of the foil is removed by etching.

At home, it uses several methods:

1. Ferric chloride. The reagent is purchased at a chemical supply store or made independently. Iron filings should be dissolved in hydrochloric acid. Before use, the solution should be kept until the iron is completely dissolved and mixed thoroughly.
2. Nitric acid.
3. An aqueous solution of sulfuric acid mixed with hydrogen peroxide tablets.
4. Copper sulphate with the addition of hot water and sodium chloride. This option is the safest, but also the longest. Throughout the entire process, the temperature of the pickle must be maintained at least 40 ° C, otherwise the pickling will last for many hours.
5. electrolytic method. You should take a dielectric container (cuvettes for developing photographs are well suited), fill it with a solution of table salt, place a board and a piece of copper foil there, which will serve as a cathode.

After etching with a liquid method, the board should be thoroughly rinsed with a solution of soda to extinguish the remaining acid.

Pickling process for other materials

In addition to metals, other materials are subjected to etching operations. Glass etching is most common for decorative purposes. Etching is carried out in vapors of hydrofluoric acid, the only one capable of dissolving glass. At the stages of preparation, a preliminary acid polishing of the surface of the product is carried out, then the contour of the future image is transferred to it. Protective coatings for glass are made from a mixture of wax, rosin and paraffins. After applying a protective coating, the workpiece is dipped into a pickling container.

The use of hydrofluoric acid creates a beautiful matt structure on the surface. To obtain a smooth, transparent surface, concentrated sulfuric acid is added to the pickling mixture. To obtain a relief, deep pattern, the operation is repeated.

Pickling Safety

In metal etching, extremely chemically active substances are used - strong acids, alkalis and their solutions. If handled incorrectly, they can cause serious bodily harm and significant property damage.

Therefore, when working with them, special precautions must be observed and the safety rules must be strictly observed during work:

• Work is carried out only in the presence of good ventilation, preferably a fume hood.
• Mandatory use of funds personal protection: rubber gloves and apron, thick industrial clothing, respirator, protective face shield.
• Do not place jars with acids and alkalis on high shelves and cabinets.
• During the dilution of acids, ACID is poured into WATER, and never - water into acid.
• When working with an acid, have a soda solution on hand, and when working with an alkali, a weak vinegar solution to wash skin areas that accidentally got drops of the solution.
• When working with the galvanic method, before starting work, carefully inspect all used electrical equipment for the absence of mechanical damage and the integrity of the insulation.
• Have a proper fire extinguisher handy.

In case of skin contact with pickling solution, immediately wash the affected area with an appropriate neutralizing solution. If acid or alkali splashes on clothing, it should be removed immediately.

If the pickling solution gets on the mucous membranes, you should immediately seek medical help. Delay in such cases can cost health or even life.