Minimal pre-processing needed

Unlike some competitive processes, Greenkote® does not require acid etching of parts before coating. If the incoming parts have lubricants, oils, or grease, those may be removed with an alkaline cleaner in a parts washer. Any scale or rust can be removed typically in a blasting cabinet. But if the incoming parts are clean, they may require no pre-processing at all.

Greenkote is ideally suited for powder metal and metal injection molded (MIM) parts. No pretreatment or sealing is required to address the residual porosity.

The Greenkote process

For Greenkote processing, parts are placed in a custom-sized steel retort along with a calculated amount of Greenkote’s proprietary metal powder. Then the retort is sealed and begins to slowly rotate while it is heated to a designated process temperature.

Greenkote’s proprietary thermal diffusion processing steps. Click graphic to enlarge.

Upon being heated, atoms of metal are diffused into the surface of the parts, growing the coating from within the surface. Through this patented thermal diffusion process Greenkote provides uniform, conformal coatings to ID and OD surfaces, blind holes, threads, filets and sharp corners. The process temperature is held for a set amount of time, depending upon the part geometry and the coating thickness, and then the retort temperature is ramped down.

After coating, the cooled parts are washed in plain city water to remove a light dust and activated in a proprietary zinc phosphating rinse. After that, the parts are simply dried and packaged for delivery. No post-processing is needed. And note that no toxic chemicals are used and no toxic wastes are generated. The little water that is used is reclaimed for reuse, making Greenkote a truly green and sustainable process from start to finish.

The specific Greenkote powder mixture together with the thermal cycle determines the final characteristics of the coating and its surface. Coating thickness can be adjusted to fit the application, from 20 to 80µm. Typical batch cycle times are 3 to 4 hours.

Parts and sizes

Greenkote processing retorts range from approximately 110 kg (250 lbs) to 6800 kg (15000 lbs) and can accommodate parts from 5 mm to 2000 mm (0.2” to 78”) in length. Larger pieces can be coated, but very large parts limit the number of items per batch which limits the throughput rate. Parts need to be able to withstand temperatures of 350-450°C.

A flexible process, both for production and development

The Greenkote thermal diffusion process is very applicable both to mass production and to smaller batch runs. It enables coating on a wide range of base metals; and other elements and powdered materials such as paints, sealers, adhesives, lubricants and more can also be incorporated into the process, allowing for innovation and development to further extend Greenkote’s performance.

Greenkote processing equipment can be used for all types of Greenkote coatings and applications. Most of the required pre/post-coating equipment can already be found in commercial coating facilities.

Greenkote^® and the Greenkote logo are registered trademarks of Greenkote PLC.