One kind of metal-Chrome
|Release time:2013-02-28 Source:admin Reads:|
As everyone knows, metal labels are made from various natural metals. One functional disadvantage of chromium plating is low cathode efficiency, which results in bad throwing power. This means it leaves a non-uniform coating, with more on edges and less in inside corners and holes. To overcome this problem the part may be over-plated and ground to size, or auxiliary anodes are used around the hard-to-plate areas. Modern "engineered coatings" do not suffer such drawbacks, which often price hard chrome out due to labor costs alone. Due to the low catholic efficiency and high solution viscosity a mist of water and chromium is released from the bath, which is toxic.
Hard chrome replacement technologies outperform hard chrome in wear resistance, corrosion resistance, and cost. By using spray deposition, uniform thickness which often requires no further polishing or machining is a standard feature of modern engineered coatings which are often composites of polymers, metals, and ceramic powders or fibers as proprietary embodiments protected by patents or as trade secrets, and thus are usually known by brand names. Hard chromium plating is subject to different types of quality requirements depending on the application, for instance, the plating on hydraulic piston rods are tested for corrosion resistance with metal labels.
To control these emissions wet scrubbers are used. The discharge from the wet scrubbers is then treated to precipitate the chromium from the solution, because it cannot be discarded in the waste water. Traditionally surface tension is measured by a stalagmometer. This method is, however, tedious and suffers from inaccuracy, and is dependent on user's experience and capabilities. Additional toxic waste that is created from chromium baths include lead chromates which form in the metal labels because lead anodes are used. Barium is also used to control the sulfate concentration, which leads to the formation of barium sulfate, a hazardous waste.