What are the methods of surface finishing?
There are several surface finishing methods that pose a unique risk to the water used during the process. These methods are as follows:
When anodizing metal, the metal parts are treated in a sulphuric acid bath. This provides a useful protective layer for metal products, but produces by-products of aluminium hydroxide and sulphuric acid. Aluminium hydroxide cannot be discharged into municipal sewers, and the EPA has strict regulations on this sewage treatment. However, the water can be flushed with a RO/DI water purification system or with a continuous flow process for large scale operations.
2: Coil coating
The coil coating process transforms long metal strips into coated coils through chemical cleaning, coating, and painting processes. Water is used at all stages of chemical treatment and the wastewater left at the end of the process contains potentially dangerous traces of chromium, lead, nickel, cyanide and other pollutants which cannot be directly discharged to the system. Water should be treated according to EPA guidelines and coil coated wastewater standards.
3: Die cast
The die casting process forms metal materials into various shapes. These processes are primarily mechanical, but produce wastewater throughout the cooling process, lubricants, and cleaning steps. Wastewater must be heated and distilled to remove traces of pollutants that are harmful to municipal sewers. By actively treating water, die casting systems can reduce waste costsand reuse distillates to further reduce waste.
4: Chemical coating
Electroless plating is a chemical reduction process that provides a uniform coating thickness on metal surfaces. This process requires large amounts of water to facilitate the required chemical reactions and the first wash step. This water is contaminated with solvents, detergents and other chemicals. The treatment process can separate or neutralize these chemicals to ensure clean water before drainage.
5: Electro polishing
In the electro polishing process, there are multiple wet stages as the polished parts move from tank to tank. As a result, process water is contaminated with lubricants, dirt and oils, and metalworking chemicals. The evaporative flash and evaporative water treatment processes can separate these pollutants so that water and pollutants can be properly disposed of.
The electroplating process produces wastewater, dangerous electrolytes, strong pickling solutions, and wastewater containing metal compounds. The galvanic wastewater treatment process can reduce the content of dangerous heavy metals in the water so that it does not exceed the maximum concentration.
The passivation process uses an acidic chemical bath to treat the surface of metal parts. This leaves traces of metal impurities and chemicals in the water. Water can be safely drained into the sewer by flushing the components and neutralizing the wastewater with alkaline chemicals.
8: Stainless steel pickling
The pickling process uses chemicals to remove high temperature scales and other imperfections from manufactured metal products. Frequently used nitric acid or hydrofluoric acid is extremely dangerous, but can be diluted to make it safe to treat and dispose of water.
At Netsol water, we strive to develop efficient and cost-effective solutions to eliminate the waste associated with various surface finishing processes. Contact us now for more information on our wastewater treatment capacity.