Pickling is a treatment used to remove impurities, such as stains, rust or scale from metal surfaces. However, as it is so powerful, pickling is difficult to control. If not strong enough, part of the stain will remain which is known as under-pickling. If too strong, the surface will be damaged which is called over-pickling.
© Fotolia, 2012
HIGH-PICK was a € 1.6 million project under the Research Fund for Coal and Steel (RFCS). This three year project which began in July 2005 made great progress in combating the over-pickling (and under-pickling) of iron by the acid solution. Reaching the "just pickled" state was precisely the objective of HIGH-PICK.
Previous to HIGH-PICK, a number of attempts had been made to monitor the pickling process but some key elements were still missing. "On-line monitoring as well as detecting under-pickling and roughness variations due to over-pickling was lacking. In addition, statistical models did not exist," says project representative, Valentina Colla, from school of excellence, Scuola Superiore Sant'Anna in Italy.
Over 36 months, the HIGH-PICK consortium comprising research, industry and education organisations in Belgium, France, Italy and Germany made great strides in obtaining high productivity and quality standards in pickling.
Under-pickling detection is now possible via a gauge or surface sensor that was successfully introduced in one of the consortium partner's pickling lines. A hydrogen-based sensor was also developed and successfully tested. In addition, the ability to analyse acid and iron content is now fully operational. Finally, a statistical model that allows a feed-back control was developed.
Better control of pickling has streamlined proceedings due to less under and over-pickling now occurring which has in turn led to cost savings and increased productivity. The ability to detect hydrogen will also avoid potential fires happening at pickling plants.
According to Colla, some of the sensors developed in HIGH-PICK such as the spectrometer array and the sensors for over and under-pickling have been commercialised with other monitoring devices reaching the technology demonstration level during the project .
Crucially, the success of the sensors could lead to commercial developments for other metal pickling processes and water-based surface treatments. This is good news for European constructors in the steel sector which tend to be SMEs.