Terry Clarke: Global Director, Decorative Products
– A Bright Future for Decorative Chromium –
Decorative Chromium electroplating has remained the most popular and widely specified metallic decorative finish for over 20 years. Its classic looks, worldwide availability and affordability have maintained it as the first choice decorative coating for engineers, designers and stylists across a wide range of decorative applications. Its use extends into many product types, from automotive parts to cell phones and its attributes, as a highly resilient decorative coating, continue to attract many new applications and uses.
Chrome is truly an iconic decorative coating adding high class impact to designs and providing a long lasting durable finish capable of withstanding even the most severe external environmental conditions for many years.
During the past 10 years, decorative chromium has enjoyed increasing appeal through the wider selection and adoption of satin effect finishes. The satin layer uniformly scatters any light falling on its surface, giving a shimmering soft bright metallic appearance. This unique micro satin effect can be adjusted from a fine sheen to a heavier matte finish depending on the design needs. The finish also retains the same performance benefits as bright chrome. Satin finishes have become a highly desirable interior trim finish for many automotive companies and continues to gain popularity as stylists seek to differentiate designs and brands.
Also complementing the bright chrome range are specialist darker chromium coatings delivered using trivalent based plating electrolytes. Finishes like Twilite® are essentially chrome alloys that have a slightly darker and warmer colour than standard chrome. Twilite® is widely used where bright chrome colours would be considered a little too monochrome or when a subtly warmer style is desired. The performance aspects of Twilite® is at least equivalent to standard chromium and in some unusual environmental conditions like Calcium Chloride, out performs standard chromium deposits.
Decoration is all about Style…
20 years ago, electroplated chrome was far less fashionable than it is today and was applied mainly to steel, brass and zinc based die cast components. Its limited appeal was partly a result of the fashions and styles of that era when the use of solid colours and colour uniformity was more popular. It was also due, in part, to the limited performance of single layer nickel/chromium electroplated coatings, especially in outdoor environments.
Today however designers and stylists are far more adventurous in their use of metallic effects, encouraged by the technical development of nickel/chromium electrodeposits, especially when applied to engineering plastics. Performance capabilities today are suited to even the most demanding external applications. Of the 60 million or so vehicles produced each year, very few models roll off the production line without being enhanced by electroplated chromium. And such is it’s styling appeal it is adopted on many of the latest consumer electronic goods as well as furniture and domestic appliances.
The long awaited 3rd Dimension – Dark Chrome
As the drive for new styles and differentiation continues, one of the challenges facing chemists and R&D specialists is the development of new fashion finishes that build upon the success of bright and satin chrome. Studies have shown that designers from different industry sectors are looking for extended chrome colour ranges, from subtle grey shades through to intense dark chrome. One of the most widely requested and anticipated development is a genuine dark chrome finish. For the most part, these requirements cannot be satisfied using top coats, lacquers, paints or varnishes even when applied over standard chrome finishes. However with the imminent launch of Moonlite, a new dark chrome finish, the range will extend from bright to satin to dark and of course any combination within these. Moonlite essentially completes the 3rd dimension in the matrix of chrome finishing options.
Beauty and Performance…
The combination of both beauty and performance may be a rare commodity but with the latest chromium coating developments, beauty and performance are truly attainable.
OEM’s recognize the value of decorative finishes and often develop specifications to ensure their specific needs are met. Technical and aesthetic requirements for decorative chromium are continually under review with expectations that higher performances for CASS, NSS, thermal cycling and Calcium Chloride corrosion resistance must be meet by new finishes.
Raising performance requirements typically raises the degree of complexity of the electroplating processes. However with good process control consistent quality is within the reach of many high volume applicators. Bright chromium originally began as a fairly simple electroplating process and has evolved into modern a process utilizing as many as 6 or 8 highly interdependent layered coatings produced using 14 or more chemical process stages. Each of these coating stages requires close chemical and operational control in order to ensure the right surface morphology is optimized to enhance specific characteristics. The final metallic layers work synergistically to optimize corrosion performance, gloss, resilience and colour. A fault at any process step can result in a significant compromise in overall performance, therefore careful process choice and control plan integrity are vital ingredients of a successful decorative plating operation.
Typical automotive OEM bright chrome performance specifications cover most of the performance criteria that electroplated chromium deposits have to offer. As can be seen below, the range of conformance testing extends from thickness measurements through to complex thermal cyclic testing designed to simulate many years of active service life. Understanding the interdependence of each process step is critical, as is operating within a carefully managed control plan. All decorative processes have optimal windows of operation within which they are capable of delivering maximum performance characteristics.
Typical OEM Specification for Plastic substrates
High performance nickel/chromium deposits applied to plastic substrates takes more than 3 hours chemical production time. The process route frequently involves 14 or more discrete chemical stages (excluding rinsing) each of which must be operated within close limits to ensure a successful coating.
The complexity of many individual processes involves the management of 3, 4 or 5 separate chemical additives, pH, temperature, agitation mode and applied current that must be controlled within tight operating ranges. This is a highly automated operation supervised by highly skilled technical staff using an increasingly sophisticated array of testing apparatus. Successful management of these systems requires detailed planning and coordination to ensure consistency.
Quality and Assurance…
Complexity adds cost therefore the applicator market is being driven to lower cost regions where labor rates make it easier to justify employing large numbers of trained technicians.
With millions of components being processed each day, the chromium plating industry is increasingly geared towards efficient mass production. Finding lower labor costs is encouraging expansion of chromium electroplating in emerging markets including China, Brazil, India, Korea and SEA. This in itself brings new challenges for a community of applicators not always experienced in working to OEM specification levels. This coupled with the divergence between local and international quality requirements places great emphasis on the technical support structures provided by key chemical suppliers. In order to ensure successful procurement of chromium decorative finishes in emerging markets, the development of supplier/applicators quality partnerships like ZinKlad and Q-Klad is vital.
These programs offer true partnerships between key applicators, technology developers, T1’s and OEM’s in which each takes an active part in ensuring process control plans are developed, implemented, monitored and maintained via agreed protocols. This tried and trusted method of collaboration is proving to be an excellent tool in supply chain management of rapidly emerging markets.
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