selective finishing of metal surfaces
what is selective coating?
The area of selective coating covers all processes during which, for technical or functional reasons, workpieces are only partially coated. While this allows for the targeted protection of component areas which are subject to heavy loads, the remaining surface remains available for other treatments (e.g. grounding).
How the area to be coated is isolated, whether by targeted coating applications or by masking certain areas of the component, is ultimately determined by the process. With LASOX-COAT® and SELGA-COAT®, Aalberts surface technologies currently offers two selective coating methods.
selective coating with SELGA-COAT®
SELGA-COAT® is a selective plating process for metal surfaces. Areas that do not require plating are covered inside a tool with a built-in sealing system. After that, an electrolyte is pumped into the tool housing. It flows around the area to be coated to galvanize it. When aluminum alloys are finished with hard anodizing processes, the workpiece is used as the anode.
selective coating with LASOX-COAT®
LASOX-COAT® is a selective coating process involving the laser-induced formation of aluminum oxide. When exposed to laser radiation, the alloy particles on the surface of the component to be processed melt and vaporize. Oxygen plasma and part of the molten aluminum react to form aluminum oxide (corundum, Al2O3), which now covers the treated surface. Underneath the corundum layer there is a remelt zone whose thickness is approximately 10 times greater.
Since the laser beam is guided across the workpiece surface section by section, the coating duration is proportionate to the area to be coated. Using this selective coating process, we can also create letterings, individual lines or complex shapes and patterns.
properties of SELGA-COAT®
SELGA-COAT® coatings on aluminum materials are partial anodizing or hard anodizing coatings and, in addition to the typical properties in terms of electrical insulation, thermal insulation, corrosion protection, and wear protection, have significantly improved properties and advantages over classically produced coatings. These include:
- fast coating time
- precise layer build-up
- low roughness
- improved hardness
- uniform structures
- no rework and pretreatment necessary
- controlled manufacturing process
- compact production line
- low material input
- sustainable closed loop system “Think GREEN – think SELGA-COAT®”
properties of LASOX-COAT®
The great advantage of selective coating methods, as opposed to electroplating processes, is the fact that they do not require any process chemicals, such as acid electrolytes. That is why it is not difficult at all to have LASOX-COAT® plants authorized. LASOX-COAT® plants are enclosed and rated as Class 4 lasers according to EN 60825-1. Therefore, they can be easily incorporated into existing production lines.
The LASOX-COAT® process increases the wear resistance of component surfaces to a significant extent. It produces extremely hard and durable aluminum oxide, because it does not create any micro-pores in the oxide layer.
In order to increase a component’s resistance to wear, it is not always necessary to coat its entire surface. Even surfaces coated in a “tartan pattern” are already more resistant to wear.
fields of application of SELGA-COAT®
SELGA-COAT® is used in various industries where a high-quality coating of aluminum is required. Especially in the automotive industry, this process has been used for years to selectively anodize different assemblies such as engine pistons, valves and pump housings. Particularly in the case of high volumes, companies benefit from the reduction of processing steps and thus a minimization of costs.
In principle, almost all aluminum alloys can be coated with SELGA-COAT®. However, it is advisable to clarify in each individual case which surface properties are to be given priority and which alloy is then suitable for the SELGA-COAT® process. Depending on the application, the coatings can be produced using Cr6-containing* or Cr6-free electrolytes.
The SELGA-COAT® process can also be adapted to other surface variants. Please contact us and we will work out a solution proposal.
*Request for authorization submitted via Hapoc GmbH & Co. KG.
base materials which can be coated with SELGA-COAT®
fields of application of LASOX-COAT®
The LASOX-COAT® process is preferably used for the selective coating of those areas of a workpiece surface which are continuously subjected to wear, such as a housing rim repeatedly hit by a cover that is opened and closed or the impeller of a pump which is subject to partial wear. Further common applications include laser markings and labeling on aluminum components for traceability and documentation purposes. The process is also used for the surface treatment of pneumatic valves, proportional valves, brake pistons, hydraulic shutters and pneumatic shutters.
base materials which can be coated with LASOX-COAT®
In general, almost all aluminum alloys may be coated with LASOX-COAT®. In individual cases, however, it is advisable to first clarify the desired surface characteristics in order to determine the type of alloy suitable for the LASOX-COAT® process.
frequently asked questions - selective coatings
In the case of the SELGA-COAT® process, work is carried out in a closed-loop system. Due to the closed circuit, employees and the environment are protected from harmful influences.
The process designated LASOX-COAT® is a selective oxidation of aluminum surfaces by laser. Since no process chemicals such as electrolytic acids are used, the process is environmentally friendly and is not subject to the usual environmental guidelines.
SELGA stands for SELective GAlvanizing. The SELGA-COAT® process is ideal for the selective galvanization of geometrically sophisticated components produced in high volumes.
During the SELGA-COAT® process, only the functional surface of the component is passed and coated by the electrolyte using electric current. The components do not have to be masked nor do they require any mechanical rework.
Any questions? Contact us directly or select a process location near you.