Environmental aspects of coil coating


Environmental aspects of the coil coating process

Coil coating is a highly industrialised process. As with any process, there are inputs and outputs and there are environmental impacts of these. 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 product itself.

Prepainted metal production has developed over the last 40 years into a very clean process. Most installations are of a size which requires permitting under various European regulations and so 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 standards to at least those regulated for at a European level.

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 turning away 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 rollercoating mean that waste is very much reduced and wastage of paint is virtually eliminated, with most potential waste being re-used in paint formulation.

Whilst some coatings can include harmful elements, the prepainted metal industry has continually evolved the coatings it uses to eliminate these. Most coatings are now produced without harmful heavy metals or hazardous solvents. Phthalate plasticisers responsible for endocrine disruption have been phased out.