ICMCTF2000 Session G7: Decorative Vacuum Coatings

Damixa A/S , a division of Masco Corporation, has introduced Brilliance^äfor the European faucet market. The development of Brilliance^ä standard has been set forth by customer demand for superior performance of brass, gold and other metallic colors. PVD processing has made this development possible and Damixa has three surface finishes conforming to Brilliance^ä and several under development.

Details on PVD technology, performance and reproducibility of coatings will be presented. Samples of deposited films are analyzed for microscopic holes and film uniformity using an electron microscope with EDX and Scanning Auger microscopy in combination with sputter profiling.

The Physical Vapour Deposition (PVD) technique is a powerful method for producing protective, hard coatings for a wide range of applications such as cutting and forming tools, architectural glass applications and microelectronics reference 1. For decorative coating applications, the use of PVD processes, when compared to traditional electrochemical plating, has caused a significant improvement in the performance of coatings reference 1,2. These improvements include well adherent, wear resistant coatings with a wide spectrum of colours. In addition to this, the growing awareness of environmental issues associated with electroplating, has resulted in the further development of combinations of PVD and electroplating techniques, for decorative applications reference 1, 2.

The major function of decorative coatings apart from giving the desired colour, is to protect the underlying substrate material from corrosion. Among various PVD methods available, the most promising and commercially available are electron beam evaporation, magnetron sputtering and vacuum arc evaporation reference 1, 2, 3. The vacuum arc deposition technique has been shown to provide a superior adhesion between the film and substrate, compared to other PVD processes reference 3. However, the arc process has found limited use in the decorative field because of the incorporation of macroparticles into the deposited coating reference 3. Subsequently, the underlying substrate can be exposed to an aggressive environment, causing failure of the coating.

The objective of this study is to investigate the corrosion performance of TiN coatings for decorative applications. The filtered arc (partial and full) deposition is combined with electrochemically deposited barrier coatings for this purpose. The filtered arc source used in this study consists of both straight and curved ducts through which a solenoidal magnetic field is produced to guide an ionised plasma through to the coating chamber. Since macroparticles have no charge, they are unaffected by this magnetic field and consequently, deposit on the sides of the ducts. The substrates employed for the coatings are typically used in commercial hardware such as brass, zinc and mild steel. The structure and composition of TiN coatings are investigated. The corrosion performance and electrochemical behaviour of TiN coating is assessed by electrochemical techniques.

¹H. Maidhof, D Hofmann, S. Kunkel, H. Schuessler, Developments in decorative coatings, 39th Annual technical Conference Proceedings, 1996 Society of Vacuum Coaters, pp. 109-113. ²G. Reiners, U. Beck, H.A. Jehn, Decorative optical coatings, Thin Solid Films, 253(1994),pp. 33-40. ³JK.C. Shimpi, K. Ravindranath, A.K. Jani, D.C. Kothari, C.S. Harindranath, Decorative coatings produced using combination of reactive arc evaporation and magnetron sputtering, Surface and Coatings Technology, 90(1997), pp. 115-122.

As reported las year the SLC (Surface-Like Chrome) - technology is a combination of powder paint techniques and an ion-assisted metallizing PVD (Physical Vapor Deposition) - process to give surfaces a high gloss, chromelike, reflective apearnace.

The SLC coating is a multilayer coating, whre a PVD - metal layer is deposited snadwichlike in between different polymer powder coats.

Apart from any kind of surface which is presently electroplated with chrome the vast range of automotive parts is possibly the biggest potential in the industry, just to name the wheel industry fo the SLC - technology.

Currently more than 100 million pieces/year are the total worldwide market for Aluminium light alloy wheels with a strong growth. Within this market there is a fast growing segment with a very high demand for bright, high gloss chrome finish. This market is already very well developed in the U.S., but also rapidly growing in Europe. The steel wheel market is even larger than the Al - wheel.

At DUROVIB Oberflächentechnik GmbH these facts were considered as a challenge to develop a high quality coating and/or process to eliminate the technical disadvantages of the existing coating processes and to offer a cost cutting alternative at the same time.

Within the last 12 montsh DUROVIB has installed an SLC - production facility for 1,000,000 wheels per year. This facility is shown in detail.

Furthermore detail of the coating process as well as coating properties are reported.