★ Main steps of cleaning before plating:
1. Degreasing Oil pollution includes three types: mineral oil, animal oil and vegetable oil. According to their chemical properties, they can be classified into two categories, namely saponified oil and non-saponified oil. Animal oils and vegetable oils are saponified oils, which can react with alkali to form soaps, which are known as saponified oils. Various mineral oils such as paraffin, vaseline, various lubricating oils, etc. They do not saponify with alkali, and are collectively referred to as non-saponified oils.
(1) Ultrasonic degreasing Ultrasonic degreasing is the mechanical force that uses ultrasonic vibration to generate tens of thousands of small bubbles in the degreasing solution. These small bubbles generate strong oscillating force during growth and closure, and the grease adheres to the surface of the material. The dirt is quickly detached, thereby accelerating the degreasing process and making the degreasing more thorough, and is more effective for treating materials having complicated shapes, micropores, blind holes, narrow slits, and high degreasing requirements. Inject a suitable amount of degreasing solution (such as dewaxed water) into the ultrasonic wave and select the appropriate temperature. Because the temperature and concentration are too high, it will hinder the propagation of ultrasonic waves and reduce the degreasing ability. In order to obtain a good degreasing effect on the depression and the face of the material, it is preferable to rotate the material in the groove so that each part can be irradiated by ultrasonic waves.
(2) Electrochemical degreasing (cathode) Electrochemical degreasing is a method in which a material is hung on a cathode of an alkaline electrolyte, and the oil is removed by the polarization of the electrode during electrolysis and a large number of bubbles generated. The polarization of the electrode can reduce the surface tension at the interface of the solution; the hydrogen bubbles and oxygen bubbles precipitated on the electrode have a strong tearing action on the oil film and mechanical agitation of the solution, thereby prompting the oil film to rapidly from the surface of the material. The upper part is turned into a fine oil bead to accelerate and strengthen the degreasing process. In addition, electrochemical degreasing not only far exceeds chemical degreasing, but also achieves a good degreasing effect that is almost completely cleaned. Increasing the current density can increase the degreasing speed and improve the deep hole degreasing quality. However, the current density and the degreasing speed are not always proportional, the current density is too high, the tank voltage is increased, and the electric energy consumption is too large. The large amount of alkali mist formed not only pollutes the air but also corrodes the material. The current density commonly used in operation is 5 & mdash; 10 amps / square decimeter. Increasing the temperature lowers the resistance of the solution, thereby increasing the conductivity, lowering the cell voltage, and conserving power. However, too high a temperature not only consumes a lot of heat, but also pollutes the environment and deteriorates conditions. An electrolyte of 60-80 ° C is usually used.
2. Washing Washing is an indispensable part of the electroplating process. The quality of the washing has a significant impact on the stability of the electroplating process and the appearance and corrosion resistance of the electroplated products. This effect comes from two aspects: First, the impurities contained in the water itself contaminate the surface of the solution or material, and the washing is not clean, causing cross-contamination or surface contamination of various materials for electroplating.
3. Weak etch (activation) After degreasing, the material will form a thin oxide film on the surface, which will affect the bonding strength between the coating and the base metal. Therefore, it should be activated before plating to cause slight corrosion on the surface of the material. The crystal structure of the metal is exposed to ensure the bonding strength between the plating layer and the substrate, and the activation solution is relatively thin, and does not damage the surface finish of the material, and the time is usually only a few seconds to one minute. (There is often a percentage of dilute sulfuric acid for activation.) The activated jewelry pieces must be washed and cleaned before plating.
★ Surface treatment process:
1. Aluminum Oxide Aluminum and aluminum alloys are easy to process and form, lighter than other metal materials, and are used more and more widely. The chemical properties of aluminum and aluminum alloys are very active and must be treated with certain protections such as electroplating, spray coating and oxidation treatment. Oxidation treatment is the easiest and most common protective treatment. The oxidation of aluminum and aluminum alloys is divided into chemical oxidation and electrochemical oxidation (commonly known as anodization). The chemical oxide film is relatively thin, soft and non-abrasive, and has a lower resistivity than the anodized film. However, the adsorption capacity is good, mainly as the bottom layer of spray paint and spray. The overall performance of aluminum anodized film is better than that of chemical oxide film. It is widely used. The main applications are: 1. Anti-expandability to improve corrosion resistance of parts 2. Wear resistance hard oxidation, HV 1200 3, insulation 4, improvement and organic Coating adhesion
Aluminium Oxidation Process: Alkaline Wash & mdash; — Wash & mdash; — Chromic Anhydride Bleach & mdash; — Wash & mdash; — Activate — — Wash — — Aluminum Oxide — — Wash —— ;—washing——closed——washed——dry
2. Nickel plating: The nickel plating on the steel substrate is a cathode coating, which can protect the steel substrate from corrosion and can be used as a protective coating for steel and the like. The bright nickel layer has good gloss and can be used as a decorative coating. In general, we use both of these uses as a protective coating. The thickness of the coating is generally 20 ~ 40mm Double-layer nickel process: chemical degreasing & mdash; — washing & mdash; & mdash; pickling rust & mdash; — washing & mdash; — electric degreasing & mdash; — washing & mdash; & mdash; ——washing——plating semi-bright nickel——plating nickel ——after immersion recycling——washing——pickling——passivation——washing&mdash ;—dry
3. Galvanizing: Galvanizing is the most commonly used steel cathodic protection coating. The coating cost is very low. It is mainly used for the conventional protection of steel parts. It is also often used as a pretreatment layer for coating in military production. After the passivation treatment of the galvanized layer, the corrosion resistance can be improved by 6 to 8 times, and the commonly used passivation layer is blunt and white blunt. The thickness of the coating is generally 7 ~ 15? m, I have adopted the alkaline zincate galvanizing process, the process is easy to control production. The plating solution has good dispersing ability and deep plating ability. The coating has fine crystals, good gloss and good adhesion to the substrate. It has partially replaced cyanide galvanizing in military production. Galvanizing process: washing & mdash; & mdash; activated & mdash; & mdash; washed & mdash; & mdash; galvanized & mdash; & mdash; galvanized & mdash; & mdash; recovery & mdash; & mdash; light & mdash; & mdash; washed & mdash; & mdash; color passivate & mdash; —white blunt ——washing——washing——drying
4. Chrome plating: Coating application 1. Decorative chrome: The corrosion resistance of chrome layer is very good, and the plating of steel parts is cathode plating. 2. Hard chrome: High hardness of chrome layer (HV800~1100), good wear resistance, 3. White chrome: Mainly used for measuring tools, indexing plates, instrument panels, hard chrome plating and white chrome plating. Directly chrome plated.
Plastic chrome process: Degreasing ——dewaxing ——washing——roughening——washing——neutral——washing——pure wash—— Dip ——activation——pure wash ——debond ——pure wash ——electroless copper ——wash ——pure wash ——copper plated &mdash ;—recycling——pure water ——plated nickel ——nickel seal recycling——washing activation——washing ——activation wash ——chrome —— Recycling ——restore——washing hot water wash
5, tin plating: tin plating process: pickling & mdash; & mdash; washing & mdash; & mdash; light & mdash; & mdash; pickling & mdash; & mdash; washing & mdash; & mdash; pure washing & mdash; & mdash; tin & mdash; & mdash; washing & mdash ;—passivation——washing——drying
6, electrophoresis: degreasing & mdash; — washing & mdash; — washing & mdash; & mdash; surface adjustment & mdash; & mdash; phosphating & mdash; & mdash; washing & mdash; & mdash; washing & mdash; & mdash; pure water washing & mdash; & mdash; pure water washing ——electrophoresis——recycling——recycling——pure water ——blowing ——preheating——cure ——pre-cooling——cooling< / p>
★ Daily maintenance procedures for solutions:
1. Zinc plating 1. The main salt (zinc oxide and sodium hydroxide) must be analyzed regularly, analyzed once every two weeks, and the main salt and zinc plate area should be adjusted according to the analysis results in time to keep the components in the normal process range. Maintain a ratio of 1/(10~12). Second, the addition of brightener is handled by a special person, according to the consumption and the quality and actual requirements of the workpiece being plated, according to the principle of a small number of times to add, and make a record of addition. DP-III and 990 brighteners are generally added in a 1:1 ratio, each time depending on the actual situation. Third, under normal conditions, a small current electrolysis treatment once a week. Filter thoroughly once a month. It is treated once every two months with CK-778 treatment. Fourth, before entering the plating tank must be cleaned to prevent contamination such as hydrochloric acid bath. 5. Use a strainer to salvage the surface of the bath every day. Sixth, the plating parts and hooks should be salvaged in time after the tank is dropped to prevent metal impurities from contaminating the plating tank. 7. The pole bar is cleaned once a week to ensure good electrical conductivity. At the same time, the copper oxide on the pole bar can be dropped into the tank to contaminate the plating solution.
2. Nickel plating 1. The main salts (nickel sulfate, nickel chloride and boric acid) must be analyzed periodically, analyzed once every two weeks, and the main salt should be adjusted according to the analysis results in time to keep the components in the normal process range. Second, the addition of brightener is handled by a special person, according to the consumption and the quality and actual requirements of the workpiece being plated, according to the principle of a small number of times to add, and make a record of addition. Bright nickel plating and semi-bright nickel are generally added at a time. 3. Under normal conditions, the small current is electrolyzed once a week, and the copper is treated twice. Filter for 3 hours a day and filter the filter twice a week. 4. Thoroughly filter the plating solution once every two weeks, and perform a large treatment every two months. 5. The pH of the plating solution should be checked every day before the first bath plating is placed in the tank, and adjusted with 10% sulfuric acid to keep the pH value in the range of 3.8~4.4. Sixth, the plating parts should be salvaged in time after the tank is dropped. 7. The plating tank should be covered before work every day to prevent dust from contaminating the plating tank. Eight, pay attention to the consumption of nickel plate, and add nickel plate in time. Nine, the pole bar is cleaned once a week to ensure good electrical conductivity, but also the copper oxide on the pole bar is dropped into the tank to contaminate the plating solution.
3. Chrome plating 1. The main components (chromic anhydride, trivalent chromium and sulfuric acid) must be analyzed regularly, analyzed once every two weeks, and the content of each component should be adjusted according to the analysis results in time to maintain within the normal process range. Second, often plating small pieces will cause low trivalent chromium in the plating solution. When the trivalent chromium is low, the electrolytic treatment is carried out for 0.5 to 2 hours by using a large cathode area and a small anode area. When the trivalent chromium is high, the electrolytic treatment is carried out for 0.5 to 2 hours by means of a large anode and a small cathode. 3. When the content of sulfuric acid in the plating solution is high, it is treated by adding barium hydroxide or barium carbonate. 1 g of sulfuric acid can be precipitated per 2 g of cesium carbonate. Be sure to clean before entering the tank to prevent hydrochloric acid and nickel, iron and other contaminated plating solution. 4. The plated parts and the hooks should be salvaged in time after being dropped to prevent metal impurities from contaminating the plating tank, and at the same time prevent the plating parts from being corroded. 5. The pole bar is cleaned once a week to ensure good electrical conductivity. At the same time, the copper oxide on the pole bar can be dropped into the tank to contaminate the plating solution.