Low-Friction Coating and Corrosion Protection Delivered with One Nanocomposite Material

Cog wheels, threads, machine parts, cranks and bicycle chains wear out, when their metallic surfaces rub against each other. Lubricants and oils can help to prevent that. But such lubricants containing fat combine with dirt and dust and agglutinate or resinify after a while. Machine parts need to be cleaned and greased in a time-consuming and expensive way — increasing maintenance and higher usage of resources or the temporary breakdown of the engines are the consequences. By using a low-friction coating free of grease, such a problem can be avoided. The researchers at Leibniz Institute for New Materials developed such a low friction coating, which also protects from corrosion.

"What is really special about our low friction coating is its composition and structure," explains Carsten Becker-Willinger, head of the program division "Nanomere". We embedded platelet-like solid-state lubricants and platelet-like particles in a binder. When the composite is applied onto a surface, a well-arranged microstructure forms, in which the various particles arrange in an imbricate structure," Becker-Willinger continues. A so-called transfer film forms between the low-friction coating and the counterpart, which allows an almost frictionless sliding of the surfaces on each other. "Only through the special ratio of components, our composite has a very low friction coefficient. If we used only the solid-state lubricant, the friction coefficient would be significantly higher," the chemist notes.

"Our low friction coating can do even more," the expert for chemical nanotechnology explains. "The imbricate structure does not only allow an almost frictionless sliding, but it also shows the effect of a barrier. This is a special advantage, as our material prevents the penetration of humidity or salts to the metal surfaces, i.e. it also prevents from corrosion." Thus, the composite shows a corrosion resistance of over 1,000 hours in the neutral salt spray test on low-alloy steel.

The low friction coating can be applied by using the conventional wet-chemical processes, such as spray or dip coating. By simple thermal curing, the imbricate structure forms in self-organization without further interference.