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Although magnesium alloys were popular in the first half of the 20th century, the bad corrosion properties prevented their breakthrough in industrial mass production. Since the technology for the production of high purity alloys was introduced in the 1970s, magnesium alloys became more and more in the focus of industrial attention. Today magnesium alloys are state‐of‐the‐art in construction parts in automotive industry. Despite its outstanding properties like good castability, low density and nearly unlimited availability the negative aspects like weak corrosion and wear behaviour still limit the application of magnesiums in industry, due to the need of sufficient surface protection (E. Aghion, B. Bronfin, Mater. Sci. Forum 2000, 350–351, 19). Today, plasma electrolytic anodisations are state‐of‐the‐art (H. Haferkamp, “Magnesiumkorrosion—Prozesse, Schutz von Anode und Kathode”, in: Moderne Beschichtungsverfahren, F.‐W. Bach, T. Duda, Eds., Wiley‐VCH, Weinheim 2000, ISBN 3‐527‐30117‐8, 242; M. Thoma, Metalloberfläche 1984, 38, 393; T. W. Jelinek, Galvanotechnik 2003, 94, 46; A. Kuhn, Galvanotechnik 2003, 94, 1114). They provide acceptable corrosion resistance and protect the magnesium from mechanical damage due to their high hardness. On the other hand, their high porosity limits their use in combination with electrochemically noble materials, leading to galvanic corrosion (J. Senf, “Untersuchung und Beschreibung von Magnesiumdruckgusslegierungen unter tribologischer, korrosiver und mechanisch‐korrosiver Beanspruchung, Berichte aus der Werkstofftechnik”, Shaker Verlag, Germany 2001, ISBN 3‐8265‐8428‐7). In addition, the high surface roughness of the plasma electrolytic anodisations restricts their use in tribological applications, particularly under sliding conditions (H. Hoche, “Grundlegende Untersuchungen zur Entwicklung von PVD‐Beschichtungen auf Magnesiumlegierungen im Hinblick auf die Erhöhung der Verschleißbeständigkeit und unter Berücksichtigung des Korrosionsverhaltens”, Dissertation, TU‐Darmstadt D17, Shaker Verlag, Germany 2004). In order to achieve smooth surfaces with high quality, the PVD technology moves into the centre of interest. Since the 1980s PVD coatings are well established and widely used for different industrial applications, mainly for steel and tool coatings. The authors were the first who carried out serious studies on the development of PVD coatings for magnesium alloys in 1999 (J. Senf, “Untersuchung und Beschreibung von Magnesiumdruckgusslegierungen unter tribologischer, korrosiver und mechanisch‐korrosiver Beanspruchung, Berichte aus der Werkstofftechnik”, Shaker Verlag, Germany 2001, ISBN 3‐8265‐8428‐7; H. Hoche, “Grundlegende Untersuchungen zur Entwicklung von PVD‐Beschichtungen auf Magnesiumlegierungen im Hinblick auf die Erhöhung der Verschleißbeständigkeit und unter Berücksichtigung des Korrosionsverhaltens”, Dissertation, TU‐Darmstadt D17, Shaker Verlag, Germany 2004). The extensive research activities lead to the recent development of a coating system, which provides ...

The authors developed a coating concept based on amorphous Si/C/N coatings, with promising high temperature properties. Due to a graded coating design, the adhesion, the coating hardness as well as the coefficient of friction were optimized. The coatings showed excellent high temperature stability against chemical decomposition, structural changes and surface oxidation up to 1 350 °C. To allow the deposition of coatings with a certain chemical composition, a numerical relationship between the composition of the coatings and the deposition parameters was established.

Although magnesium alloys became popular in the first half of the 20 th century, the bad corrosion properties prevented their breakthrough in industrial mass production. Since the technology for the production of high purity alloys was introduced in the 1970s, magnesium alloys became more and more in the focus of industrial attention. Today magnesium alloys are state of the art in structural parts in automotive industry. Despite its outstanding properties like good castability, low density and nearly unlimited availability the negative aspects like weak corrosion and wear behaviour still limit the application of magnesium in industry [1].So, the only economic solution is the deposition of a coating or a suitable surface treatment which provides both, wear and corrosion resistance. Today, plasma electrolytic anodisations are state of the art [2 -5]. They provide acceptable corrosion resistance and protect the magnesium from mechanical damage due to their high hardness. On the other hand, their high porosity limits their use in combination with electrochemically noble materials, leading to galvanic corrosion [6]. In addition, the high surface roughness of the plasma electrolytic anodisations restricts their use in tribological applications, particularly under dry sliding conditions [7].On the other hand, due to the high life time recommendations the application of magnesium in the automotive industries motion component field is a long term process. Nevertheless, there is a quite high industrial interest to apply magnesium in the motion component field in consumer applications like do-it-yourself or gardenig. Some examples are motor components of lawnmovers, motor saws or drills. Especially for these fields of application there are quite high demands on the corrosion properties due to undefined storage and the conditions during usage.In order to achieve smooth surfaces with high quality, the PVD technology moves into the centre of interest. Since the 1980s PVD coatings are well established and widely used for different industrial applications, mainly for steel and tool coatings. The authors were the first who carried out serious studies on the development of PVD coatings for magnesium alloys since 1999 [6,7].The extensive research activities lead to the recent development of a coating system, which provides both, good wear properties as well as good corrosion behaviour.

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