Robert Boschgmbh

Bernhard Blaich

Ernst Zehender

Karl Kerner

Helmut Stein

The present invention provides a process for preparing silicon oxide layers on a substrate, and particularly on metal, having improved corrosion-protective properties. This is accomplished by making the silicon oxide protective layer hydrophobic, preferably by incorporating therein hydrophobic organosilicon residues. The protective layers are preferably prepared by vapor deposition in a vessel containing silicon and/or silicon oxides in the gasous form, oxygen, and a organosilicon compound containing at least one hydrophobic group bonded to the silicon.

Silicon oxide coated metal having improved corrosion resistance

The reflectors, for example for automotive vehicle head lamps are reflectorized by evaporating aluminum thereon in a vacuum vessel at a vacuum of about 10.sup.-7 bar; thereafter, and without removing the reflectors, a gaseous monomer is introduced raising the pressure to about 5 .times. 10.sup.-6 bar to deposit a protective layer by polymerization from the gaseous phase. The monomer gases, preferably, are low molecular weight siloxanes having methyl-, vinyl- or phenyl groups, preferably hexamethyldisiloxane (HMDS), or methyl-, vinyl- or alkoxy silanes, preferably vinyltrimethylsilane (VTMS), polymerization being accelerated and ensured by an electrical discharge generated within the vessel by a heated electron emitter placed at a negative voltage with respect to the reflector blanks. After polymerization, the layer is rendered hydrophilic by treatment with oxygen at a pressure of about 10.sup.-2 to 10.sup.-3 m bar to form an organosilicon polymeric protective layer which is inherently hydrophobic and has a hydrophilic surface.

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Stuttgart, Germany

Bernhard Blaich