Electroplating is the deposition of a
metallic coating onto an object. Electroplating is achieved by passing an
electrical current through a solution containing dissolved metal ions and the
metal object to be plated. The metal object serves as the cathode in an
electrochemical cell, attracting metal ions from the solution. Ferrous and
non-ferrous metal objects are plated with a variety of metals, including aluminum, tin, bronze, cadmium, copper, chromium, iron, lead, nickel, zinc, as well as precious metals, such as gold, platinum, and silver.
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Electroplating process:
The process involves an important pretreatment step in order to
guarantee the quality of the plating (cleaning, removal of greases,...). The
pretreatment step requires a large solvent use such as chlorinated plus
surface stripping agent. After that, there are the plating, rinsing,
passivating and drying steps.
The following schematic summarizes the main steps of the
electroplating process:
Wastewater composition:
Almost all the substances and products used in electroplating can be
found in the wastewater, for instance acidic solutions, toxic metals,
solvents, and cyanides. This contamination is a consequence of the different
process steps such as spillage, rinsing, dumping of process baths. Basically
the wastewater contain is high in heavy metals, cyanides, fluorides, oil and
greases.
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Wastewater treatment:
Even if all the electroplating plants have their own level of
contamination and pollution there are a several common treatment steps:
cyanide destruction, filtration
of suspended solids, evaporation, flow equalization and neutralization, pH
adjustment for precipitation, heavy metal removal and
so on.
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Rabu, 3 Oktober 2012
Electroplating
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