Nanocomposite Coating Shows Low Friction and Corrosion Protection
A nanocomposite coating that protects from corrosion and also shows lubrication properties similar to grease and oil - such a material has been developed by researchers from Leibniz Institute for New Materials in Saarbruecken, Germany. The new material is suitable for the coating of metals and metal alloys, such as steel, aluminium or magnesium.
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 INM developed such a low-friction coating, which also protects from corrosion.
The Transfer Film
The most striking feature of the coating is its composition and structure, explains Carsten Becker-Willinger, head of the program division "Nanomere". Platelet-like solid-state lubricants and platelet-like particles are embedded 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. 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. Due to the special ratio of components, the nanocomposite coating has a very low friction coefficient. If a solid-state lubricant is used, the friction coefficient would be significantly higher.
Protection from Corrosion
However, the low friction coating can do even more: 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 the nanocomposite 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 nanocomposite 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.
From 23 to 27 April 2012, the researchers present these and further results at the trade fair "Research and Technology" in Hanover, Germany.