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Selective coatings

Selective coatings

Selective finishing of metal surfaces

Can customers also partially apply coatings themselves?

Can customers also partially apply coatings themselves?

Yes, Aalberts surface treatment specialises in designing LASOX-COAT® and SELGA-COAT® systems for installation in their customers' existing production lines.

LASOX-COAT®

LASOX-COAT® is a selective oxidation of aluminium surfaces using a laser. In an oxygen atmosphere, a laser beam is directed onto the surface of the workpiece to be treated. Under the influence of the laser, alloy particles begin to melt and vaporise. The oxygen plasma, which consists of ionised atoms, and part of the molten aluminium react to form aluminium oxide (corundum, Al2O3), which now covers the treated surface. Below the corundum layer, the remelt zone is about 10 times thicker.

The laser beam traverses the surface of the component, back and forth, like a farmer ploughing his field. The coating time is therefore proportional to the coating area, or in other words: the smaller the area, the faster the processing. The selective coating process can be used to create labels, individual lines or complex shapes as well as patterns.

The LASOX-COAT® plant is enclosed and designated as laser class 4 under the EN 60825-1 standard. The big advantage over galvanic processes is the absence of process chemicals such as electrolyte acids. Therefore, the approval of a LASOX-COAT® plant poses no problems. This is particularly interesting with regard to the integration of a LASOX-COAT® plant into an existing production line.

  • Properties

    The spacing of the tracks produced by the laser beam, as one can easily imagine, affects the degree of coverage and the roughness of the treated surface. The roughness is more than twice as high with cross web direction as in web direction.

    The hardness of the aluminium oxide is very high because the process does not form micropores in the aluminium oxide layer. The hardness of the remelting zone depends on the alloy used.

    LASOX-COAT® coatings considerably increase the wear protection of the component surfaces. To increase wear protection, a surface does not always have to be completely coated; even a "cross-hatch" pattern makes a surface more wear-resistant.

  • base material

    Basically, almost all aluminium alloys can be coated with LASOX-COAT®. However, in individual cases, it is, advisable to clarify which surface properties should be prioritised and which alloy is suitable for the LASOX-COAT® process in that case.

  • Application

    LASOX-COAT® is mostly used for partial wear protection of aluminium components, but can also be used to reduce corrosion on a workpiece. Flat surfaces are preferable, but rounded surfaces are also coatable. Small coating surface areas of a large component are ideal because then the locally generated heat can dissipate well.

    A typical application example for a coating with a LASOX-COAT® layer is a part of a component surface which is subject to repeated wear. This can be a housing edge on which a flap strikes when opening and closing or a pump impeller that partially wears. Laser markings and laser writing of aluminium components for the purpose of traceability and documentation are also conceivable.

    Further application examples include pneumatic valves, proportional valves, brake pistons, hydraulic and pneumatic slide valves.

SELGA-COAT®

SELGA-COAT® is a process for the selective galvanic finishing of metal surfaces. Defined surface areas are precisely treated. Component surface areas which are to be left uncoated are covered, inside a tool, with an integrated sealing system. An electrolyte is pumped from a reservoir into the tool and it passes between the free component surface and the tool housing. With aluminium alloys as a base material, the component surface is connected as an anode in a circuit with the tool housing opposite. Then a partial hard anodising layer is generated on defined areas of the component.

  • Properties

    SELGA-COAT® coatings on aluminium materials are partial hard anodised coatings and have significantly improved properties over classically produced coatings, e.g. excellent opacity, increased corrosion resistance, coating hardness, rapid layer build-up, more uniform microstructures, greatly improved levelling ability, significantly lower roughening and significantly higher purity.

    After partial finishing of the surface using the SELGA-COAT® process, mechanical reworking can be dispensed with in most cases.

  • base material

    SELGA-COAT® (selective hard anodising) is suitable for the treatment of wrought, cast, and die-cast aluminium alloys.

  • Application

    The main potential for coating with the SELGA-COAT® process is in the automotive industry and in mechanical engineering because, on the one hand, components are manufactured in large numbers and, on the other hand, the requirements for the coatings are very demanding.

    SELGA-COAT® (selective hard anodising) has already proven itself excellently in the partial coating of vehicle parts, amongst other things, with brake system components, clutch components, engine pistons (diesel, petrol), pump housings (power steering), wheel hubs and bearings, valves (eg. injection pumps), valve piston (automatic transmission), intermediate plates (automatic transmission).

    Aalberts surface treatment also specialises in designing SELGA-COAT® systems for installation in existing production lines of their customers.
  • Process Locations

    Aalberts Surface Treatment Sp.z o.o.

    ul. Strefowa 5
    58-200 Dzierżoniów
    Polen

    Tel.: +48 74 8108508

    Write an email

    Aalberts Surface Treatment SAS

    Avenue Bade Wurtemberg
    57380 Faulquemont
    Frankreich

    Tel.: +33 387 00438 0
    Fax: +33 387 94300 8

    Write an email

SELGA-COAT® CHROME

If partial metal is to be deposited then the component surface is connected as a cathode in the circuit opposite to the tool housing.

The SELGA-COAT® CHROME coating takes place in an enclosed system, i.e. there are no open containers with chromic acid solution. Plant operators do not come into contact with hexavalent chromium. In addition, the plant is operated without wastewater and with almost complete recycling of the chemicals used. Thus, the disposal of used chemicals is reduced to a minimum.

In view of the fact that, under the EU chemicals regulation REACH, in most cases, hexavalent chromium should not be used as of September 2017, the selective, environmentally friendly SELGA-COAT® CHROME process offers an opportunity for an exception.

  • Properties

    The special feature of the SELGA-COAT® CHROME process is that it operates at a much higher current density compared to normal hard chrome. This results in the following properties: a very high deposition rate, high layer hardness, increased corrosion resistance, low roughness and very narrow coating tolerances.

  • base material

    The SELGA-COAT® CHROME process hard chromium plates unalloyed or hardened steel components.

  • Application

    Rotationally symmetrical, preferably elongated components such as axes, spindles, shafts or tubes are suitable for hard chrome plating using the SELGA-COAT® CHROME process. Of course, any other component made from unalloyed or hardened steel can be hard chromium plated, if selective coating makes sense.

  • Process Locations

    Aalberts Surface Treatment SAS

    Avenue Bade Wurtemberg
    57380 Faulquemont
    Frankreich

    Tel.: +33 387 00438 0
    Fax: +33 387 94300 8

    Write an email

SELGA-COAT® GOLD

In the case of selective coatings of gold the component surface is also connected as a cathode.

  • Properties

    SELGA-COAT® GOLD coatings, like gold layers, generally have high ductility, tarnish resistance, good solderability and low specific electrical resistivity.

  • base material

    Almost all metals and metal alloys can be gold plated using the SELGA-COAT® GOLD process.

  • Properties

    SELGA-COAT® GOLD coatings are primarily intended for electrical contact components. Very high demands are placed on the reliability of the connections of contact points in electronic devices, which can usually only be achieved with a gold coating. A precise partial coating also helps to minimise gold consumption and thus reduce costs.

  • Process Locations

    Aalberts Surface Treatment SAS

    Avenue Bade Wurtemberg
    57380 Faulquemont
    Frankreich

    Tel.: +33 387 00438 0
    Fax: +33 387 94300 8

    Write an email

Product enquiry

If you would like to tell us something about the product presented here, you are welcome to do so. Your enquiry, your comment, your wishes will be forwarded directly to your personal contact person.

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