Metal corrosion signs can be divided into aluminum plate, stainless steel plate and copper plate according to the material. According to the production effect, it can be roughly divided into three types: concave plate, convex plate and convex concave combination. There are three basic requirements for corrosion label: beautiful design, clear line, suitable depth, flat bottom, full color, uniform wire drawing, uniform surface color. The characteristics of corrosion resistant label are: weather resistance, strong solvent resistance, even if the paint falls off, it still has the function of name plate.

1、 Making principle of metal corrosion label


The anti-corrosion ink used for metal corrosion signs must have the following requirements: fine ink with easy screen printing, small rheology, no pinhole, clear image, firm bonding with the board, corrosion resistance, easy to remove the ink after corrosion, etc. corrosion resistant ink can be roughly divided into two types: screen printing anti-corrosion imaging ink; UV imaging anti-corrosion ink.


1. Screen printing anti-corrosion imaging ink:


Ink can be divided into three types: corrosion resistance:


a. Acid corrosion resistance;


b. Alkali corrosion resistance;


c. It is resistant to acid and alkali corrosion.


1. Acid corrosion resistance after the ink corrosion, use alkali solution to remove the film. Ink use is relatively simple, screen printing speed is fast, suitable for mass production. Acid resistant ink is also divided into two types: self drying and thermosetting. The particles are relatively thick, there are many pinholes after printing, and the image is rough, which needs careful modification. The corrosion resistance is poor, and time and labor are required. The label is suitable for larger patterns, but the price is lower. Thermosetting ink particles are fine, which is suitable for fine screen printing. It has almost no pinholes and has a fine image. Baking ink in the corrosion-resistant components floating on the surface of the ink layer, so corrosion resistance is very strong. It is suitable for fine patterns and signs requiring deep corrosion, but the price is higher than that of self drying ink.


2. Alkali resistant etching ink is mainly used to protect the oxide film after aluminum oxidation, remove other oxide film for reoxidation and dyeing, and remove ink with solvent. It is suitable for mobile phone shell, cosmetics packaging, high-end product name plate, etc.


3. Acid and alkali resistant etching ink. Because of its fine ink, uniform luster and strong weather resistance, the ink can be used instead of the topcoat. It is mainly used for the corrosion of concave signs. The method is to print ink on metal. After baking and solidification of the screen printed plate, the alkaline oxide solution is removed to remove the metal oxide film, and then the acid etching solution is used for corrosion. After the completion of corrosion, there is no need to remove the ink, which is characterized by fast production, time-saving and labor-saving, and does not need to remove repeatedly. Film damage to metal surface.


4. UV imaging ink, also known as photosensitive blue oil, metal photosensitive glue, photosensitive ink, etc., is characterized by UV imaging, fine pattern, strong corrosion resistance, empty screen for printing, and spray gun. Compared with traditional bone glue, it consumes less power, saves labor and time, does not need glue, does not need manual glue, does not need high temperature baking, and the ink utilization rate can reach 98 %According to the label material, UV imaging ink is divided into two types. Type: special photosensitive ink for stainless steel plate, titanium plate, copper plate, aluminum plate.


5. Stainless steel plate and titanium plate have corrosion resistance requirements for the adhesion of photosensitive ink due to their smooth surface, otherwise the corrosion resistance is very poor. However, the stronger the metal adhesion of ink is, the later ink removal is relatively difficult. Fortunately, stainless steel plate, titanium plate and copper plate are resistant to sodium hydroxide strong alkaline solution corrosion, identification signs, neon lights, billboards, light boxes, outdoor advertising, acrylic acid can be used in the At high temperature, in a strong alkali solution of 60-80 ° C, the removal of the film will not cause damage to the metal surface.


6. Special photosensitive ink for aluminum plate, because the corrosion of our current corrosion-resistant metal photosensitive ink needs to be removed with strong alkaline sodium hydroxide solution, but aluminum will quickly corrode in the strong alkali solution, that is to say, the flatness and smoothness of aluminum surface paint will be destroyed, and the color paint will be burned. Especially when the electrophoretic paint filling machine is used for painting, the paint must be painted first and then the ink must be removed. The ink is usually removed and the electrophoretic paint is stripped together. The reason is not that the electrophoretic paint is not resistant to alkali solution, but the strong alkaline solution quickly corrodes the aluminum plate, and the side etching is carried out in parallel to pick up the electrophoretic paint from the periphery. The key to solve this problem is to change the properties of metal photosensitive ink to maintain the original viscosity. In combination with metal fastness, namely acid corrosion resistance, it can quickly dissolve in weak alkaline solution without damaging the surface of aluminum material. The filled electrophoretic film will not fall off. In order to solve this problem, we have repeatedly studied and tested the preparation of special additives (CHO) for the photosensitive ink of aluminum plate. This problem can be completely solved. For example, in the case of blue oil, 20-25g assistant is added to each kilogram of ink, printed or sprayed on aluminum plate, through baking - Printing - developing - washing - corrosion - washing - electrophoresis- Baking to remove photosensitive ink is very simple, aluminum surface is not damaged, electrophoresis paint is still hard and glossy.

No matter what kind of metal you use on photosensitive ink, you must pay attention to the following problems:


1. The metal must be completely degreased, cleaned, dried or naturally dried;


2. Printing or spraying photosensitive ink must be a uniform ink layer, thinner and better under the premise of corrosion resistance;


3. The baking temperature should be strictly in accordance with the requirements of the ink manufacturer;


4. Special printing equipment should be used for the plate light source, and the printing time should be slightly longer than the data provided by the ink manufacturer; the temperature of the developer should be kept at 30-40 ℃, not too high;


5. Different etching solutions should be used for the same metal plate. The principle is as low as possible, the corrosion rate is fast, and the side corrosion is small;


6. The corrosion machine shall be of high-pressure jet type. The features of the machine are: low temperature of corrosive solution, fast corrosion rate, small side corrosion, high utilization rate of corrosive liquid and little damage to ink.


3. For several problems of metal corrosion liquid, the selection of corrosion solution for label should follow the economic, environmental protection, low temperature, fast corrosion rate, small side corrosion, flat bottom surface after corrosion, small damage to corrosion-resistant ink, and can be recycled. The principle of metal corrosion is divided into electrochemical corrosion and chemical corrosion. Our corrosion of metal signs is usually chemical corrosion, also known as micro battery corrosion. The corrosive medium is acidic and alkaline, and most of the signs are acidic.


1, aluminum corrosion solution, aluminum is a kind of active metal, has a strong affinity with oxygen, can quickly form oxide film in air and water. Due to the presence of oxide film, aluminum has a strong corrosion resistance. Therefore, a certain proportion of active ions should be added into the corrosive liquid of aluminum to destroy the oxide film first and then corrode. The corrosion process of aluminum is dual, which can be alkaline corrosion and acid corrosion.

2、 Corrosion manufacturing technology of aluminum label


The corrosion of aluminum in corrosive liquid can be divided into three processes


In the step, the oxide film is destroyed, and the active ions in the etching solution are crushed by high-pressure pump pressure injection. With the corrosion going on, all the oxide films are separated;


In the second step, pitting, because the alumina film gradually falls off under the action of active ions in the etching solution, the secondary exposed metal is corroded, and pitting corrosion is formed, and the result of pitting corrosion leads to uneven metal surface. It is necessary to avoid corrosion of metal signs.


The third step is uniform corrosion. Due to the separation of alumina film from the angle of complete separation in the corrosion process, although pitting corrosion is formed, a certain amount of etchant is added to the etching solution, and the high-pressure pump is used for high-pressure rinsing. The oxide film and corroded metal ions are quickly removed from the corrosion area to achieve uniform corrosion.
Aluminum has a pH value of 4.5-8.5 in the passivation zone, and the passivation film is not easy to be corroded. When the pH is less than 4.5, it is acidic corrosion; when the pH is greater than 8.5, it is alkaline corrosion, because most of the protective ink used for label corrosion is acid resistant, so most of the corrosive liquid used is also acidic. The lower the pH of acidic corrosive liquid, the faster the corrosion. Taking nitric acid etching solution as an example, when the concentration reaches 30%, the corrosion rate is faster when the temperature is higher than 15 ℃. If the concentration increases, the corrosion rate decreases. When nitric acid reaches 80%, there is almost no corrosion.
The main component of aluminum corrosion solution is made up of oxidant, activator, leveling agent and water in a certain proportion. As the corrosive liquid is water by naked eyes, it should be poured into the corrosive machine immediately or pasted with obvious signs to avoid unnecessary damage to personnel.

3、 Corrosion process of stainless steel and titanium plate


(1) Stainless steel label corrosion liquid, stainless steel is a special material, with good resistance to atmospheric and fresh water medium corrosion, wire drawing, corrosion, polishing can obtain good decorative effect. However, stainless steel corrosion is much more difficult than copper and aluminum. The fast corrosion method is electrochemical corrosion, also known as electrolytic corrosion. Due to electrochemical corrosion, the ink falls off in the process of label corrosion. The label is not suitable for electrochemical corrosion, especially for fine patterns. We only choose chemical corrosion. Chemical corrosion can be roughly divided into two types: strong acid corrosion and ferric chloride corrosion. Due to the strong acid corrosion, difficult maintenance and large amount of smoke, the polluted air is harmful to human body. Manufacturers without purification equipment cannot use it. Ferric chloride corrosion formula is simple, easy to maintain and regenerate.


Ferric chloride corrosion stainless steel formula: ferric chloride, active agent, water, Bomei ferric chloride in the formula should be kept at about 42, 0.8-1.2 ml of active agent per liter of hydrogen chloride solution, the formula of stainless steel bottom surface is smooth and smooth, without black passivation film and pitting corrosion.


The factors affecting the corrosion of stainless steel by ferric chloride solution are as follows:


1. The influence of concentration and chemical corrosion is also called micro cell corrosion. The more positive the redox potential, the faster the corrosion rate. With the increase of concentration, the redox potential becomes more positive, and the industrial grade is trichloride. Because of its low purity, its redox potential is relatively low. Only when it reaches 42 or higher, the redox potential can meet the requirements of stainless steel corrosion.


2. The influence of pH value on the corrosion rate of the solution is that the pH value is low, and the stainless steel is highly corrosive; the excessive pH value of ferric chloride is hydrolyzed into iron hydroxide precipitation, and the corrosion is lost. The pH value of corrosive liquid should be adjusted to a certain extent in production.


3. The influence of etching solution temperature. The higher the temperature of corrosive liquid, the faster the corrosion rate. However, considering the corrosion resistance of the ink, the temperature should be controlled between 30-40 ℃.


4. The influence of corrosion equipment on corrosion rate. Theoretically, the higher the pressure of corrosive liquid, the faster the corrosion rate. Under the condition of high pressure, the corrosion rate of metal is improved rapidly, and the corrosion rate of metal is improved under high pressure.


5, the influence of stainless steel passivation film on the corrosion rate, we often encounter a layer of Black Gel deposited on the surface of stainless steel corrosion zone electrostatic corrosion and splash corrosion, the deposition of film corrosion rate rapidly decline, even if the corrosion metal surface is also sand paper particles, and will not cause corrosion.


6. To solve this problem: firstly, adjust the pH value of corrosive liquid properly; secondly, increase the pressure of corrosive liquid. In the pressure corrosion process, the deposited passive film can be impacted from the corrosion area, which is also a method.


The corrosion of titanium plate and titanium plate is almost the same as that of stainless steel plate. The titanium plate used in the label is actually vacuum plated with thin titanium film on the surface of stainless steel, and is processed into golden yellow by oxidation and dyeing. Its purpose is to protect and decorate stainless steel plates. The production of titanium label has higher requirements for ink, because the surface of gold plate is smooth, the oxide film is not easy to combine with ink, so titanium coating needs to be removed by strong oxidant. Therefore, titanium plate should be selected. It is a kind of ink with good adhesion and strong oxidation resistance.


7. The production method is as follows: firstly, remove the oil stains and impurities on the surface of titanium plate, print patterns or photos, then solidify the ink, quickly add a strong oxidant (1-2 seconds) to erode the titanium coating, take it out immediately and wash it with water. Check that the titanium coating is clean and the ink is turned off. After passing the inspection, corrosion can be carried out by etching the stainless steel label. The regeneration of stainless steel etching solution is to improve the redox potential and adjust the pH value of the etching solution. Add appropriate amount of hydrogen peroxide and hydrochloric acid.

4、 Corrosion process of copper plate label


Copper plate is divided into pure copper plate and brass plate. Pure copper is often called copper. Because of its simplicity and elegance, color is mainly used in high-end products, such as high-end furniture nameplates, musical instrument nameplates, sculpture nameplates, etc., most of which are not polished or filled with paint or old processing. Brass signs are widely used for brand cards, travel cards and equipment nameplates. Copper plate has many corrosion formulas, which is more economical and practical as ferric chloride solution. Ferric chloride melts with tap water, the Baume degree is adjusted between 36-42, and the temperature is controlled at 25-40 ℃. Although the higher the temperature, the faster the corrosion rate, but the ink and equipment bearing capacity should be considered. One of the great advantages is that copper ions can be electrolyzed from the solution by direct current electrolysis, and the solution can be reused by pouring the solution into the plastic tank. The anode is connected to the lead plate, and the carbon rod suspended on the cathode is introduced. The 12V DC current and copper metal ions will be adsorbed on the carbon rod of the cathode.


Because the copper plate is more corrosive than the stainless steel plate, the waste liquid which corrodes the stainless steel plate can also be used for the copper plate corrosion. In order to pursue the bright effect after the corrosion of copper plate and the original color of copper plate, it can also be corroded by using chromium trioxide and sodium chloride solution.


The formula is as follows:


50 g chromium oxide, 400 g sodium chloride, 1 L water, temperature 20 ° C, attention: chromium trioxide is sexual! It should be strictly protected in the process of deployment and use, and the workshop must be ventilated.

5、 Corrosion equipment problems.


The chemical corrosion equipment used in the label is rogue type, splash type, center rotating suction type and high-pressure spray type. Some manufacturers use electronic circuit board automatic conveying corrosion machine as metal label corrosion machine.


1. Rogue corrosion machine. The corrosion machine is welded with PVC material. The upper part is an open groove with a certain inclination. The plate is located at the bottom of the groove and corrosive liquid flows through the pump on the label. The machine has the advantages of simple design and low cost. The cost is low, but the corrosion rate is slow, the side corrosion is serious, and the passive film is easy to form in the corrosion area, which affects the corrosion.


2. Spatter corrosion machine, which passes through a shaft at the bottom of the corrosion tank and welds three splash scoops on three parts of the cross section of the shaft, which is driven by the rotation of the shaft. electric machinery. The splashing spoon spills corrosive liquid on the label to prevent corrosion. The cost of the machine is low and the design is simple. The disadvantage is that the splashing spoon is easy to be knocked off by the falling label, and the maintenance is very troublesome; the side corrosion is heavy, and the corrosion is easy. Production of passive film.


3, the central rotary suction spray corrosion machine, the corrosion machine is a hexagonal deep trough, placed in the middle of a hollow tube, drilling on the wall of a dense hole, the lower end of the pipe is divided into water. The wheel is equipped with pulley at the upper end, and the bearing is fixed by angle iron. The corrosive liquid is drawn into the pipe through the rotation of the motor, and then sprayed through a small hole in the pipe wall to corrode the marks placed on the groove wall. The corrosion rate of the first two sections of the device is fast and the cost is relatively low. The disadvantages are that the liquid pressure is too small, the bottom corrosion is not smooth enough, and there is side corrosion.


4. Electronic circuit board automatic conveying corrosion machine. The corrosion machine is specially designed for electronic circuit board. Due to the slow corrosion speed and low hydraulic pressure, the conveying roller can not bear the weight of the label and similar metal label corrosion is not suitable.


5. High pressure spray corrosion machine. There are three types of vertical, horizontal and automatic transmission. Its main advantages are: high pressure spray corrosion rate, low temperature of corrosion liquid, high utilization rate of corrosion liquid, slight corrosion of side, smooth bottom surface after corrosion, low maintenance rate, and automatic temperature control device. The disadvantage is that the price is high.


In short, in order to produce the ideal label, we must improve the equipment, ink, consumables and production process.