Environmental aspects of the coil coating process

Coil coating is a highly industrialised and controlled process with a number of inputs and outputs. Inputs to the process include metal substrates, paint, pre-treatment chemicals, water and of course energy. Outputs include solid waste, effluent and vapour emissions in addition to the prepainted product itself.

Prepainted metal production has developed over the last 50 years into a very clean process. Most installations are of a size which require a licence to operate under various European regulations; the coil coating process is carried out under very tightly controlled conditions. Unlike many smaller post-coating operations, this provides an assured level of environmental compliance to both national and European regulations.

The environmental impacts of the coil coating process include:

Energy: used to provide motive power and, the largest part, in heat to cure the coatings. Emissions of volatile organics are very tightly controlled by the coil coating process to the extent that they are virtually eliminated. In many cases, this is a primary factor in small fabricators converting from post-painting to using prepainted metal. Water - used in rinsing, mostly at the cleaning / pre-treatment stages and for quenching. However, most modern lines use a cascading rinse system to minimise water usage and discharges. The continuous nature of the coil coating process and the efficiency of roller-coating mean that general waste is very much reduced and paint wastage virtually eliminated. The small amount of paint waste is usually recycled into fresh paint formulations. The industry is fully REACH compliant and has successfully eliminated a number of chemicals such as chromium VI in response to their use being prohibited under the REACH process.

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Introduction to the coil coating process