The CRM Group has completed the development of a Cr-free surface conversion treatment named “Silicalloy”, with a first successful industrial application. Silicalloy is applicable in continuous high productive lines on metals and galvanised products.
The concept was originally developed for the final passivation step in galvanisation lines as a cheap and environmentally-friendly alternative to chromatation. However, it has since then demonstrated remarkable surface conversion properties in many applications before painting.
In galvanizing lines, where it is implemented just after the zinc bath, the strip is quenched into a batch containing a colloidal suspension of suitable nanoparticles.Thanks to the strip heat, the solution is locally destabilized and the nanoparticles precipitate onto the metal. The result is an ultrathin coating (50-200 nm), very compact, that provides excellent paint adhesion and anticorrosion properties. This process combines speed (< 1 s) and robustness.