Etching is the key to the pattern decoration process of the metal plate mold. In order to obtain a pattern product with clear stripes and strong decorativeness, attention must be paid to controlling the conditions of the etching process. Mainly the temperature of the etching solution and the etching time. A slightly higher solution temperature can increase the rate of metal dissolution, that is, the rate of etching, and shorten the time required for etching. However, the etching solution is generally a strong acid solution. The strong acid solution is highly corrosive at high temperatures and is easy to protect The coating or corrosion-resistant ink softens or even dissolves, so that the adhesion of the corrosion-resistant layer of the non-etched part of the metal is reduced, which causes the corrosion-resistant coating at the junction of etching and non-etching to fall off or melt, which makes the etching pattern blurred and distorted, affecting the pattern Because of its beautiful appearance and decorative effect, the temperature should not exceed 45℃. Similarly, if the etching time is too long, especially when the temperature of the etching solution is high, the immersion time of the corrosion-resistant ink or the protective coating is too long, it will also have the aforementioned side effects and adverse consequences, so the time control should be appropriate , Can not be soaked for too long, generally should not exceed 20-25min.
(4) Examples of chemical etching pattern decoration
1. Decorative materials
Decorative metal plates: ordinary steel, stainless steel, copper and copper alloys, aluminum and aluminum alloys, etc., take the stainless steel plate as an example, and the plate thickness is 1 to 3mm.
Chemical raw materials: screen printing photosensitive glue (such as DH diazonium type produced by Zhejiang Kunshan Chemical Coating Factory), acid-resistant inks are 99-956 type and 99-200K type (products of Guangdong Shunde Daliang Ink Factory), others are commonly used chemical chemicals drug.
2. Process flow
Stainless steel plate → degreasing → washing → drying → screen printing → drying → water immersion → etching pattern leaf (sheet) washing → deinking → washing → polishing → washing → coloring → washing leaf (sheet) hardening treatment → sealing treatment → Wash the leaves (sheets) to dry → inspect → product.
3. Specific operations and precautions
(1) Degreasing Degreasing is to make the screen printing ink have a good adhesion to the plate, so the metal plate must be completely degreasing before printing. There are many degreasing methods, which can be selected according to the situation and needs. For example, conventional chemical degreasing, surfactant degreasing, or even electro-degreasing, ultrasonic degreasing, etc. can be used. Commercial special degreasing agents can also be used. After thoroughly cleaning, it is dried and then transferred to screen printing.
(2) Screen printing uses 150 mesh stainless steel, polyester or nylon monofilament nets, fixed on the screen frame with a stretcher, and then squeezes DH diazo photosensitive glue with a sizing machine, and coats it for 2 to 3 times. After the coating film is dried, attach the photographed black and white film with the pattern to the coating screen. After exposure and development, the screen printing template is prepared, and then the stainless steel plate and the pattern template are fixed on the corresponding position of the screen printing machine. , Use alkali-soluble, acid-resistant ink to print the required patterns and dry (or dry) naturally. If baking, the temperature should not be too high and the time should not be too long, otherwise the alkali solubility of the ink will decrease, and it will not be easy to clean up when the ink is removed. Under normal circumstances, dry naturally for 1 hour. Drying at 55～60℃, 4～5min.
(3) Pattern etching process The formula and process conditions of pattern chemical etching solution are as follows:
Iron chloride (FeCl3) 650～800g/L etching accelerator 85～lO0g/L
Hydrochloric acid (HCl, 38%) 85～120g/L etching solution temperature 10～45℃
Phosphoric acid (H3P04) 20～30g/L Dipping time 15～25min
Strictly control the temperature and time of the solution during operation. If the temperature is too high or the time is too long, the adhesion between the ink and the board surface will decrease, and the ink may fall off at the etched and non-etched places, resulting in blurry patterns, affecting the accuracy of the etching and the decorative effect.
(4) Ink removal after etching After etching, the protective alkali-soluble acid-resistant ink must be removed. The method is to immerse in 40～60g/L NaOH lye, the temperature is controlled at 60～70℃, soak for 3～5min, whichever is the clean ink. Then rinse the lye on the surface with water to neutrality. (5) Post-etching treatment After the etched patterned stainless steel plate has been de-inked and cleaned, the following additional decoration treatments can be made according to the different needs of users.
①For those that require the preservation of the original color and gloss of stainless steel, after removing the ink and cleaning, put it in a solution of 50% HN03 (volume fraction) and 50% H20 for 10-20 minutes for passivation treatment to make the stainless steel etching pattern board Get a new protective film, you can get decorative products.
②For those that require the preservation of the original color of stainless steel, but require higher brightness and brightness, after removing the ink and washing, electrolytic polishing is performed first, and then the surface is passivated.
The solution formula and process conditions of electrolytic polishing are as follows:
Citric acid 50%～70% solution temperature 40～60℃
Sulfuric acid 20%～l5% current density 15～30A/dm2
Water 10%～25% Polishing time 5～10min
Cathode material lead plate
③In order to improve the decoration of products, some users require to change the color of the original stainless steel. In this regard, after the stainless steel is etched and the ink on the surface is cleaned, it is electropolished and then chemically or electrolytically colored. After coloring, the colored film must be hardened and sealed to obtain the desired decorative products. The formula and process conditions of the chemical coloring solution are as follows:
Sulfuric acid (H2S04) 270～300g/L, solution temperature 65～80℃
Chromic anhydride (Cr03) 450～500g/L The processing time is from blue to orange to golden
(NH4)6Mo7024·4H2040～50g/L color-green, color changes with time
After chemical coloring, a hardening treatment (or solid film) is required to stabilize the colored film and improve the quality and wear resistance of the colored film. The solution formula and process conditions of the hardening treatment are as follows:
Potassium dichromate (K2Cr207) 10～20g/L solution temperature 65～80℃
Sodium hydroxide (NaOH) 3～5g/L treatment time 2～3min
After the above-mentioned hardening (solid film) treatment of the colored film, the hardness, abrasion resistance and corrosion resistance have been improved, but the film layer has pores, and further sealing treatment is required. If the colored film itself is of good quality and high hardness, hardening treatment is not necessary, but sealing treatment must be performed. The composition and process conditions of the sealing solution are as follows:
Sodium silicate (Na2Si03) 10g/L solution temperature 100℃
Boiling sodium dodecylbenzene sulfonate 2～5g/L, treatment time 4～6m
In addition to chemical coloring, electrolytic coloring can also be used. The formula and process conditions of the electrolytic coloring solution are as follows:
Chromic anhydride (Cr03) 80～260g/L Current density 0.05～0.10A/dm2
Sulfuric acid (H2S04) 25% (volume fraction) Coloring time l0～30min
Solution temperature 70～90℃
In the coloring process of this coloring solution, the process conditions have a greater impact on the color. The first is the effect of the concentration ratio of sulfuric acid to chromic anhydride on the color. When the concentration of chromic anhydride is high, it is golden yellow, and when the concentration is high, it becomes purple-red. The effect of temperature on coloring is: as the temperature increases, the color gradually deepens. The effect of the coloring time is: the coloring starts at 5 minutes, and the color deepens with the increase of time, and the color is basically stable after 20 minutes. The effect of current density on coloring is: at 0.03A/dm2, it is rose, and at 0.05A/din2, it is 18K gold.
Hardening treatment is also required after electrolytic coloring. The hardening treatment can be done by chemical methods (for example, above) or electrolytic method. The solution formula and process conditions of the electrolytic hardening treatment are as follows:
Chromic anhydride (Cr03) 240～280g/L Cathode current density 0.2～1.0A/dm2
Sulfuric acid (H2S04) 2～3g/L anode material lead or lead-antimony alloy
Solution temperature 50～55℃ Treatment time 10～15min
After the hardening treatment, it should also be sealed, boiled in a boiling sodium silicate solution for 5 minutes, taken out for cleaning, and dried to obtain decorative boards with various colors and luster.