Electroplating

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.

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.

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.