Summary
Hot-dip galvanising plants use cold rolled steel strip as a base material. Upon delivery, this material will generally show some residual surface contamination from the rolling process. This contamination will need to be removed by further surface treatment, if the adhesion of the functional coating to be applied to the metal surface during the hot dipping process is not to be impaired.
The strip cleaning process which is generally applied at present involves the heavy consumption of water, chemicals and energy.
The object of this project was the industrial implementation and operational commissioning of a high-pressure and ultrasonic strip cleaning process for the minimisation, not only of environmental pollution, but also of product and production costs.
Results:
- For roller emulsion residues, high-pressure cleaning achieved high levels of decontamination (> 80%). In combination with ultrasonic cleaning, these values can be substantially improved. In the case of iron contamination, high-pressure cleaning achieved decontamination levels in excess of 92%. In this case, the combination of this process with ultrasonic cleaning produced only limited improvements.
- By the application of high-pressure cleaning technology as a replacement for mechanical brush cleaning, both procurement and disposal costs for brushes can be eliminated. In tandem with electrolytic cleaning, ultrasonic cleaning can achieved the desired decontamination performance with lower energy consumption.
- The strip cleaning process tested is characterised by a high degree of efficiency, in combination with a significant saving in the consumption of cleaning chemicals. In consequence, both the costs and energy consumption associated with wastewater cleaning can be reduced.
