A sprayed coating ensures a smooth glide while protecting against rust. Photo: Uwe Bellhäuser

Materials
researchers from Saarbruecken in Germany have developed a low friction
coating combining two properties: It shows lubrication properties
similar to grease and oil and it protects from corrosion. The new
material is suitable for the coating of metals and metal alloys, such as
steel, aluminium or magnesium. From April 23-27, 2012, the researchers
from INM—Leibniz Institute for New Materials will be presenting these
and further results at the trade fair “Research and Technology”.

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.

“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 says.

“Our
low friction coating can do even more,” he 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.

Source: INM – Leibniz