Passivation and pre-treatment of metal in one step

Metal surfaces can be passivated and pre-treated in just one step. The RoHS-compliant and chromium III-based new product Bonderite M CR 1405 gives coils excellent corrosion resistance.

When treating metal surfaces, there are traditionally two different lines: one for pre-treatment and one for passivation. In the conventional process, parts are either sent directly to the end user or on to the painting line after passivation. Rust protection oil is used before painting, which must be removed in the subsequent cleaning and rinsing stage. If a passivation layer is applied, rinsing is sufficient before the subsequent paint application.

With a new development from Henkel, users can significantly shorten their processes: Bonderite M CR 1405 has unique properties, as it can be used both as a passivation for bare substrates and as a pre-treatment for painted substrates. After passivation, the coils are either forwarded directly to the end user or for painting. Bonderite M CR 1405 has good recoatability. Passivated coils can be used in the coating line without a cleaning step and only require rinsing with hot water to remove impurities. This leads to considerable savings in energy and water consumption, as the cleaner that is now no longer required is normally used in large tanks at temperatures between 60 and 70 degrees Celsius. The elimination of chemical cleaning agents also significantly reduces waste water pollution.

This combination is made possible by a newly developed product: Bonderite M CR 1405, a chromium III-based passivation pretreatment, combines both processes. "If a passivated coil is painted without post-treatment, sufficient paint adhesion and corrosion resistance is generally not achieved. Conversely, a pre-treatment that is used as a passivation usually fails within a day," says Gerko Odink, Senior Manager PD Metals EU at Henkel Adhesive Technologies. "Here we have a product that combines the best of both worlds and is compatible with both chrome-containing and chrome-free primers."

As it is a chromium III-based product, it meets the performance expectations of users for high corrosion protection and is also RoHS-compliant ("Restriction of certain Hazardous Substances"). This directive prohibits the use of hexavalent chromium in Europe. "We close the gap between legislation and performance by using a bridging technology that meets the requirements for architectural applications, for example," says Gerko Odink. The test on galvanized and Galvalume substrates shows a bare corrosion resistance of more than 96 hours. The salt spray test shows a resistance of 800 hours with a chrome primer and 500 hours with a chrome-free primer.

By reducing the number of process steps and the associated energy and water consumption, the new product is in line with Henkel's long-standing commitment to sustainability. "Enabling safer, cleaner and more efficient processes is at the heart of our business," says Volker Mansfeld, Vice President Industry EIMEA at Henkel Adhesive Technologies. "Together with our customers, we strive to rethink designs and processes to identify opportunities for sustainable innovation and defossilization of the industry while delivering the highest level of performance." (OM-3/25)