Electroplating plastic – the highest level of surface finishing
Metallic looking surfaces have enjoyed a great popularity for many years now. There is already a trend in the automotive industry for high-gloss or matte chrome plated switches, fittings and trims. The same also goes for the area of “white goods”, for electrical installations and for numerous other industries in which an attractive appearance, and therefore also electroplating, is becoming increasingly important. Plastic electroplating, also known as plastic metallization, produces high-quality and elegant surfaces which captivate people because of the refined optics and metallic haptics. Products which are electroplated include radiator grills, mirror caps, fittings and door handles on cars, for example, but products such as cell phones, shower heads and buttons on Hi-Fi systems are also coated in this way. The main customer for electroplated plastic components has been and still is the automotive industry, where the relevant components are used in both the interior and on the exterior of vehicles.
Plastic metallization – the advantages
The electroplating of finished plastic parts combines the characteristics of the plastic with that of the metal used in a unique way. An important reason for electroplating plastic, alongside the look and feel of the finished product, is the saving in weight. This is particularly relevant in the automotive branch, where each gram counts, but also for numerous everyday objects which must look perfect but also be comfortably light weighted. Whether it be gold, silver or chrome, matte, gloss or brushed – electroplating provides almost limitless design possibilities which can make attractive products out of simple plastic blanks. In addition, there are also several technical advantages such as increased corrosion protection, adhesive strength, thermal conductivity, friction reduction, temperature and weather resistance, soldering and bonding capacity, as well as abrasion and scratch resistance. Furthermore, plastic metallization can be used for “shielding” against electrosmog without the plastic casing of electrical and electronic devices being permeable for electromagnetic waves. Electroplating creates thin but extremely dense layers with ideal damping values which open up numerous fields of application for functional, electroplated plastic parts ranging from components for the automotive industry, for the electrical industry and even for household items like furniture fittings, video and photography cameras and jewelry and watches.
Plastic as a base material
What makes plastic metallization so unique is the material that you start out with. In comparison to metal, not only is plastic a cheaper alternative, but it is lighter too. With regards to form and design, it can be adapted to almost all of the wishes of the designers and customers without any further processing through costly grinding or polishing required. Plastics such as ABS/PC-ABS or fiber-reinforced plastics are primarily used for plastic electroplating. ABS is the abbreviation for acrylonitrile butadiene styrene. PC stands for polycarbonate. PC-ABS is a blend of both of these original materials which combines the processability of ABS with the mechanical characteristics of polycarbonate (e.g. making the product heat and impact resistant). Extremely precise, selective metal coating makes it possible to work with multi-component plastics, whereby they are made suitable for special applications. Polyamides (PA) are also commonly used for electroplating as they have a high level of resistance and toughness and are therefore predestined for a variety of suitable areas of application.
Electroplating plastics – how it works
Electroplating is when an electrolytic coating is added to the surface of a plastic. For this to work successfully, there needs to be a sufficient amount of adhesion between the plastic and metal layer. To ensure this, the plastic components are first of all chemically pre-treated in various processes.
Pre-treatment of the plastic components
With plastic parts made from acrylonitrile butadiene styrene, the butadiene is first dissolved out from the resin matrix on the surface. This results in the creation of tiny cavities which form the basis for the adhesion of the metal coating. In the activation step, palladium nuclei are inserted into the empty spaces and are then transformed into conductive palladium in a subsequent reduction.
The actual electroplating process
After the pre-treatment, a thin layer of nickel is chemically, i.e. without current, deposited on the plastic part, therefore manufacturing the electrical conductivity. To avoid adhesion problems occurring during the electroplating of plastic and to optimize the current transfer with the subsequent electrolysis, this nickel layer is galvanically reinforced. Subsequently, the components are placed in a copper sulfate solution, in which they accumulate a layer of copper through an exchange of charges. On the one hand, this makes the surface more conductive, and on the other, it prevents the nickel layer from breaking. In addition, this layer provides for the thermal growth compensation at increasing temperatures, where plastic and metal behave in significantly different ways. Furthermore, the copper layer has a levelling and smoothing effect. After this step in the electroplating process, various different layers of nickel can be added to the plastic parts either individually or in a combination. This is what causes the difference between the degree of matte and gloss of the material surface, for example. Finally, the chrome layer is applied. This layer guarantees protection against wear and fulfils high demands regarding corrosion resistance. The ultimate overall strength of the metal layer depends on the later intended use. The higher the strain on the product, the higher the overall layer strength of the plastic electroplating should be.
Keune & Lauber, for the highest quality demands in electroplating
As an experienced partner in plastic metallization, Keune & Lauber GmbH has an extensive system and process know-how when it comes to plastic electroplating. Whether it be high-gloss, matte chrome or black chrome – with surface finishes done using electroplating, we are able to give a wide variety of plastics an extremely appealing yet functional optic. To do this, we have an 80-meter-long process-controlled electroplating system which has a particularly environmentally-friendly technology concept. In order to guarantee stable processes for plastic electroplating, we regularly check the electroplating electrolytes in our modern, in-house laboratory and the chemicals that we use are supplemented with the help of the analysis results. Our experienced electroplating technicians, innovative system control and resource-saving technology all guarantee a high-quality surface finish. After processing, all electroplated components are extensively tested with the most modern testing and measuring devices in compliance with all regulations and norms to ensure an appealing surface appearance and a long service life.
Electroplating and the environment – ecological aspects in the foreground
The processes and procedures used during the plastic electroplating require the materials used to be handled very carefully. Therefore, the environment and safety are always at the forefront of our thoughts and actions. Thanks to our technically sophisticated electroplating equipment, we are becoming increasingly successful at keeping the effects of our production on the environment to a minimum. All waste water resulting from the process baths is processed in a modern water treatment plant. Any investigations relating to this are subject to monitoring by external laboratories and the relevant authorities. An exhaust air purification supplements the aforementioned waste water treatment.