With the burnishing gels of the Nigrit series, the German specialist for metal chemistry is expanding its portfolio in the application area of etching, pickling and burnishing. Like the liquid variants, the gels can be used for cold burnishing, marking and blackening on a wide range of metals and alloys as well as high-alloy stainless steels.

To create a black colouration or permanent marking on metallic surfaces, Emil Otto GmbH offers a range of different burnishing agents, which are now also available for individual formulations as viscous gels. “With the previous liquid burnishing agents, larger surfaces can be processed reliably and quickly. The new gels, on the other hand, allow for pinpoint processing of the workpiece to be treated. Since the gel does not run, it works exactly where the employee has applied it,” explains Markus Geßner, responsible for marketing and sales at Emil Otto GmbH. This precise direct dosing is especially important when component surfaces have to be processed that actually have to be removed for burnishing or blackening. “This step is no longer necessary,” Geßner continues.

The Nigrit gels are available for various metal surfaces. In addition to stainless steel, aluminium, iron, steel, copper and brass, bronze can also be processed. When the workpieces are processed, black mixed oxide layers are formed that protect the surface. These can also serve as corrosion protection in the case of iron, steel and stainless steel. The layers created by burnishing are resistant to bending and abrasion, which makes subsequent further processing of the metal possible. The layer can only be removed mechanically.

“Depending on the material, a relatively quick blackening occurs approx. 5-30 seconds after application. If the workpiece remains in contact with the nigrit gel for longer, loose oxides accumulate on the surface and are removed after the process,” Geßner explains further. To remove these oxides, Emil Otto offers Neutrasol, a product developed specifically for this purpose. Afterwards, the workpiece has to be dried and preserved. Emil Otto also has a suitable product for preservation in its range. The after-treatment fluid is a temporarily effective, preserving metal protection that can be applied thinly after the gel has been used. All burnishing agents, whether in liquid or viscous form, are intended for immediate use in metal processing.