Patent Application
20120164350
The present invention relates to the field of coatings. More specifically, it relates to a process for the treatment of parts which allows combining different shiny and matte finishes in one and the same part.
Chromium coatings by electrolytic baths are currently used as a decorative layer protecting against corrosion. These coatings are generally made with electrolytic baths.
In these conventional baths, plastics are not conductors, therefore they require being subjected to complex pretreatment process in order to be able to receive the coatings.
New methods for chrome plating by means of physical vapor deposition (PVD) which allow using less toxic products are currently being developed. PVD technology starts directly from the solid material which is to be deposited to then convert it into vapor by means of heating it or bombarding it with energetic ions. The vapor formed condenses on the surface of the substrate, forming a thin layer. The process is performed under vacuum or in a controlled atmosphere to prevent the interaction of the metal vapor with the air. A coating process by means of this method is described in patent application ES 2 239 907 A1.
In order to create a chrome plating, either on plastic or on metal surfaces, copper is first deposited on the surface of the product. This layer is about 20 to 25 microns thick. A deposition of nickel of approximately 15 microns is then carried out and finally the chromium is applied with a typical thickness of about 0.5 microns. In the event that a matte appearance is to be conferred, the last layer of nickel is matted before applying the chromium. However, if the part is to have matte and shiny areas, the area or areas with an appearance different from the majority of the part should be independently inserted, giving rise to an additional complexity. Currently, matte areas can be achieved with the application of organic layers in a partial manner on the chrome-plated shiny surface. This solution has problems of definition in the border of the different finishes and of resistance with respect to the outdoor demands required in automotive applications such as adherence, scratch resistance, etc.
The object of the invention is to solve the technical problems mentioned in the previous section. To that end, it proposes a process for the treatment of parts to give to the surface different glazed and shiny finishes.
The process comprises, on the surface previously coated with a first layer of copper and a second layer of metal, performing a selective etching of the second layer, in which this selective etching is performed according to the area or areas to be matted with respect to the rest of the part. The selective etching can be performed by means of a laser which goes over the surface matting the desired area or areas. The laser is preferably a Yag laser with a wavelength of 1064 nm and a power of 100 W. The selective etching can alternatively be performed by scraping or chemically, in which case the areas which must be shiny are protected. In the case of the chemical etching, a masking coating is applied on the surface or surfaces which must be shiny, the masks being dissolved with a solvent after the selective etching on the exposed areas.
The second layer of metal can be of nickel or of nickel and chromium on the latter. In the first case, the layer of nickel is etched whereas in the second case the layer of chromium is etched. After the selective etching, another layer of non-corrodible metal (once again chromium, steel or metals such as Zr, Au, Pt, Rt, In, etc.) is applied. These metals can be applied to the part by PVD or any other suitable technique. The chromium can also be applied by electrolysis, both before being etched and in the final step.
The process of the invention is applied to parts made of plastic material and of metal, for example those treated with a layer of copper and nickel as a preparation for the chrome plating process. In a first embodiment, the partial surface etching is performed on the layer of nickel, which allows obtaining contiguous areas with a different texture/shine. The part is then chrome-plated, with galvanic chromium, for example.
In another embodiment, the part has the layers of copper, nickel and chromium, the layer of chromium being superficially etched.
The selective etching can be performed in both cases by chemical methods (with acids) or physical methods, for example with a laser or by scraping the unprotected areas, creating textures or shine (glazing) different from those previously protected.
If the etching is chemical or by scraping, the areas which must not be treated and which will be shiny are protected with protections or masks, the protections being removed afterwards.
Finally, a layer of non-corrodible metal can be applied using PVD technology (sputtering, arc, etc.), the preservation of the different levels of shine or texture obtained being assured as above. The metals used in this last step are chromium, titanium, zirconium, indium, ruthenium or noble metals such as gold or platinum. The different metals give to the part a finish with different colors, the glazed appearance of the areas previously treated by means of the selective etching being respected and the part being protected from external aggressions. The final finish of the non-shiny areas can have different mesh or geometric shapes, the use of laser being preferable for this particular example. For striped finishes, etching by scraping is preferable.
The chromium applied both in the intermediate step and in the last step can be galvanic chromium or chromium applied by PVD.
By means of this process, it is achieved that one and the same part has areas with different finishes without needing to introduce detachable elements in different areas of the main part or use organic layers partially applied on the metal and facilitating that the surface of the part is homogeneous and resistant to outdoor and indoor requirements, for example those of the automotive industry. The finish therefore has areas with a different shine depending on the etching time and the method used (from mirror shine to matte including glazing and all the intermediate tones) the differences in thickness of which cannot be observed by the human eye without optical aids.
By selective etching it is understood that the areas to be treated are previously selected and altered such that the texture and shine of the previously deposited layer of nickel or chromium are partially modified. This gives to the selected surface an appearance different from the base shiny appearance.
The selective etching with laser is performed with a Yag laser with a wavelength of 1064 nm and a power of 100 W, for example.
It would be possible to implement the application with other types of laser with similar features.
Various finishes can be achieved by controlling the power and the action time of the laser, which gives different nuances to the part, from a more mirror-like tone (shiny area) to a more or less matte finish or with a specific texture.
The etching can alternatively be performed with acid after masking the surfaces which must be shiny. The masks are subsequently removed with a solvent. The masking in the case of chemical etching is performed with special paints resistant to the chemical products used during the surface etching phase.
If the etching is performed with scraping, the protections are applied by painting, by mechanical masks or by means of pad printing.
| Number | Date | Country | Kind |
|---|---|---|---|
| P200930637 | Aug 2009 | ES | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2010/062558 | 8/27/2010 | WO | 00 | 3/5/2012 |
