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Selective galvanic finishing of metal surfaces

What fascinates us about hummingbirds?

What fascinates us about hummingbirds?

Hummingbirds can drink nectar very quickly and precisely, through their long beaks, in a fascinating hovering flight without touching the flowers. We direct electrolytes through components in a precise manner. Thus only specifically defined points come into contact with the electrolyte.

The process

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. If partial metal is to be deposited then the component surface is connected as a cathode in the circuit opposite to the tool housing. Currently, AHC offers the partial deposition of hard chrome (SELGA-COAT® CHROM) and Gold (SELGA-COAT® GOLD).

The SELGA-COAT® CHROM coating takes place in an enclosed system, ie 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® CHROM process offers an opportunity for an exception.

  • Characteristics

    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.

    The special feature of the SELGA-COAT® CHROM 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.

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

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

  • Base Materials

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

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

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

  • Field of 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).

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

    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.

    AHC also specialises in designing SELGA-COAT® systems for installation in existing production lines of their customers.

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.

More Surface Treatments



    Hard anodisation, hard coating

    to the process


    Optimisation of frictional processes by means of specially structured metal surfaces

    to the process


    Partial oxidation of aluminium surfaces without the use of chemicals

    to the process


    Hard anodising with fluoropolymers

    to the process

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Aalberts Industries