Methods 1: chromium was removed by special machinery.
1, using a grinding sandblasting machine. Abrasive sandblasting machines that use sand blasting and shot blasting can use particulate powder or fine particles to grind materials. Car beauty shops and construction companies are usually equipped with this equipment. Long-term grinding and sandblasting can remove the chrome coating of the object, but after that, some hard-to-reach areas may need to be treated separately. In order to avoid damage to the underlying metal, it is best to use materials with relatively small particles, such as 400 # sand, when sandblasting the chromium plating layer.
Note that in the process of using the sandblasting machine, the chrome-plated layer will be ground into small pieces and fall off, thus forming dust and deposits in the air. They are poisonous, so we must take appropriate measures to protect our faces and mouths.
2. Use ultrasonic cleaning machine. Ultrasonic cleaning machine is a special kind of equipment, which uses sound waves to clean delicate articles such as jewelry, which are difficult to clean. In some cases, the ultrasonic cleaning machine can even remove the chromium coating. If you loosen the chromium plating layer in other ways, its cleaning effect will be better. Put the chrome-plated articles into the cleaning tank of the ultrasonic cleaning machine and soak them in the cleaning solution. The solution used in ultrasonic cleaning machine is usually ordinary tap water. Then follow the instructions to turn on the cleaning machine. As mentioned above, replacing water with a solvent that can dissolve chromium, such as bleach, can enhance the chromium removal effect of ultrasonic cleaning machine. However, before doing so, please ensure that this solvent will not corrode the cleaning machine or react with it in any other way. For example, as described below, lye will react with aluminum containers.
Please note that although ultrasonic cleaning machines come in various sizes, most of them can only accommodate relatively small items, such as jewelry, hub nuts, tools, decorations and so on.
Method 2: remove chromium with chemical solution.
1, with hydrochloric acid (hydrochloric acid). Hydrochloric acid is also called hydrochloric acid, which makes it a strong acid and corrosive. Using high concentration hydrochloric acid, the chromium plating layer on metal objects can be removed. A concentration of about 30-40% should be enough. The operation method is as follows: in a large barrel for mixing chemical raw materials, such as a corrosion-resistant plastic barrel, hydrochloric acid and water are mixed according to the ratio of 1∶3 to obtain a 30% acid solution. You can also buy a prefabricated acid solution with the required concentration.
Immerse the chrome-plated object in the solution until the chrome-plated layer falls off.
Wash objects thoroughly with soap and water, and then dry them.
2. Use sodium hydroxide (alkaline solution) to remove chromium plating on ferrous metal and carbon steel. Sodium hydroxide, commonly known as lye, is a corrosive alkaline chemical. It can dissolve several metal coatings, including chromium, but it will have dangerous chemical reactions with water and aluminum. It will corrode aluminum objects and produce flammable hydrogen. Therefore, it can only be used for articles whose base materials do not contain aluminum. The operation method is as follows: in a vat made of neutral raw materials such as corrosion-resistant plastic buckets, 250 ml to 350 ml of sodium hydroxide and 4 liters of water are mixed.
Immerse the chrome-plated object in the solution until the chrome-plated layer falls off. This may take a long time, so be sure to check the peeling of chromium plating layer frequently.
Wash objects thoroughly with soap and water, and then dry them.
3. Carry out reverse electroplating. Chromium is attached to the metal surface by electroplating process. During electroplating, the current will combine chromium and metal at the molecular level. Reversing this process can remove chromium plating layer very effectively. However, this is very dangerous. Because this process requires electricity, and the reaction products also contain several toxic carcinogenic chemicals. For example, hexavalent chromium is an extremely dangerous product. Therefore, this method is best used by professionals. The following steps are for reference only. Chromic acid and sulfuric acid are mixed in water at a ratio of about100:1. For example, 950 grams of chromic acid crystals and 9.5 ml of sulfuric acid solution were added to distilled water to prepare a 4 liter solution. When preparing the solution, electroplating, material testing and chemical treatment must be carried out in an appropriate immersion tank.
Heat the solution. When the decorative chromium plating layer is removed, the temperature of the solution is kept at 35 to 46 degrees Celsius. When hard chromium is removed, the temperature is kept at 49 to 66 degrees Celsius.
The negative charge of DC power supply is introduced into the chromium plating solution through wires.
Connect the positive electrode to the object from which the chromium coating is to be removed and immerse it in the solution. Chromium metal with positive charge on the surface will fall off the surface of the object.
Rinse the items in the drum with tap water, and then rinse again. Professional treatment and disposal of waste.