Alternatives to traditional electroplated chrome have hit the market that can achieve the material’s bright and glossy look without the negatives usually associated with electroplating. The timing couldn’t be better.

Chrome has traditionally been a symbol of luxury and affluence, whether it is found on an expensive car or as a decorative item that accentuates an appliance. While its popularity has gone in and out of fashion over the years, it appears that the chrome look is back and more popular than ever, as a trip to an automotive dealership or high-end appliance retailer can attest.

Traditionally, chrome was applied to metal by an electroplating process; parts were either sprayed or dipped in heavy-metal chemical baths. This process is fraught with health and environmental concerns, however, as well as escalating costs.

BSH Appliances used Soliant’s film to gives the knobs, buttons, and other decorative parts on the clothes washer a chrome appearance.

Production plating lines carry a huge price tag to build and operate because of the cost of complying with federal regulations governing the chemicals used in the process. The most popular of which is hexavalent chrome, which offers superior durability and corrosion resistance as compared to other chromium products such as trivalent, which is a naturally occurring chrome. Hexavalent chrome is produced industrially when trivalent chrome is heated in the presence of acids and minerals and atmospheric oxygen. In this form, fumes and particulates are released into the atmosphere and are considered carcinogenic.

Due to those concerns, OSHA set an exposure requirement of less than five micrograms per cubic meter over an 8-hour period. Manufacturers are required to capture the chromium released into the air and regularly test the air to ensure that they are in compliance. In addition, the “platers” must treat waste water and handle chromium slag generated during the finishing process.

Hexavalent chrome was one of six materials banned by the European Union’s under its Restriction on Hazardous Substances directive (RoHS). In addition to health concerns, the EU is concerned about hexavalent chrome’s impact on the environment as products with the hexavalent chrome enter the waste stream. While research differs, there is concern about the material ending up in soil and groundwater. According to the EPA, about half of all Superfund sites, those sites with particularly egregious environmental problems, have excessive levels of the chromium. In one case highlighted by the movie Erin Brockovich, hexavalent chrome was found in the drinking water consumed by residents of Hinkley, Calif. The material, which was used to fight corrosion in the cooling towers of a utility facility, was linked to cancer and other negative health effects in the community.

Soliant offers a number of color and brushed chrome looks.

Because of Europe’s restrictions, and compliance issues in the U.S., the number of plating facilities has dwindled; an important issue for OEMs who outsource their electroplating needs. This lower capacity is expected to escalate costs for an already costly process.

The process can also be time consuming, creating bottlenecks in production, as raw metals need to be polished and machined to smoothness before multiple layers of metals can be applied. A copper layer is often applied over aluminum and plastic substrates to promote adhesion. Then, up to eight layers of nickel are applied before the chrome is coated onto the part. All this can add up to increased costs to OEM customers.

At the same time that traditional chrome plating is getting more difficult to use, the chrome look has become popular again with consumers. Fortunately, new options give designers the opportunity to achieve the high-end look of chrome using environmentally friendly, easy-to-use, and cost-effective processes. These alternatives include physical deposition processes that condense chrome alloys on a metal or plastic substrate, decorative laminate films that adhere to multiple substrates, and plastics with a molded-in metallic look. These approaches give the part the look of chrome, and, in some cases, the feel of it.

Bayer’s Metallic FG Makrofol film can give a product a chrome appearance.

The metal deposition process is probably the costliest process, but best looking option. This process can coat metal or plastic substrates with thin layers of chrome alloys and as the chrome isn’t in an oxidized state — it is not a hexavalent chrome and is not covered under the EU’s directives.

With this technology, the manufacturer can achieve the same appearance as traditional chrome plating, even when compared side by side with a traditional electroplated chrome part. In the past, if a chrome-coated plastic part and a ferrous part were used, they would look different, and the designer would have to build that into the design. Previously, designers had to use “distinct lines” to separate ferrous and non-ferrous parts, but with this technology no distinct break lines are needed.

Two companies that are offering this technology in an effort to mimic chrome are Goodrich Technology of Pittsburg, Calif., and American Trim, Lima, Ohio. Goodrich, which was one of the earliest users of the process, coats its parts in 30 in. diameter physical vapor deposition batch chambers for a four layer, multi-step process. Goodrich coats parts for its customers, but is looking to license its technology to other manufacturers. Patrick Colahan, vice president of Goodrich, says that a wide variety of substrates can be used including aluminum, bronze, brass, steel, and magnesium.

Soliant’s Fluorex paintfilms, a precursor to the company’s Bright Film, decorate these cell phone components.

American Trim uses a PVD chamber that measures 6 ft. in diameter and 12 ft. in length. The chamber is the centerpiece of the Advanced Materials Commercialization Center developed in partnership with the James A. Rhodes State College, also of Lima. The facility is designed to attract development programs for PVD production and can supply sample parts and prove out the technology to interested OEMs. The facility operates at a throughput rate of about 1 to 10 percent of what actual production is estimated to be, says Steve Hatkevich, director of research and development for American Trim. The low throughput rate is the result of the need to build flexibility into the line to allow the simulation of PVD coatings of a variety of parts, large and small, in various complex shapes.

Unlike the electroplating process that requires the metal surfaces be buffed and polished to smoothness, both companies use a primer that eliminates this step. The primer coats the surface and levels off surface irregularities so the metalized layer can be applied, says Owen Decker, a product manager for DuPont Powder Coatings, Houston, which makes the Smoothcoat primer used by American Trim.

Metals such as aluminum or steel are powder coated, while plastics are sprayed with a UV-curable coating because the plastics are not as resistant to the high temperatures typically required for curing powder coatings, adds Colahan. The UV coating creates a cross-linked network that promotes adhesion of the metalized layer, prevents out gassing from the base plastic, and smoothes the surface, adds Hatkevich.

A bumper uses the American Trim PVD process. Inset are the layers of the process. Including the base substrate, smooth coat primer, metalized film layer and protective topcoat.

The magnetron sputtering process in use is a cool to warm processing system. Under most circumstances the part temperature does not exceed 100 DegF, and rarely rises above 150 DegF. Thus, most substrates can be processed. With sputtering, atoms are dislodged from the surface of a material as a result of a collision with high-energy particles. The atoms then condense on the substrate as a thin film.

After receiving the smoothing base coat, the part, or batch of parts, is placed into the sputtering vacuum chamber. The chamber is then drawn down to a vacuum. For instance, American Trim uses a vacuum pressure of around 5.0 x 10 -5 Torr. The chamber is then flooded with argon gas, and the magnetron is energized. The magnetron applies a negative voltage, about -300 V, to the target, which is the chrome material that will be applied to the substrate.

This negative voltage attracts the positive argon ions to the target surface, bombarding the surface and ejecting the chrome material atom by atom. A “plasma” gas is created, sometimes called a “glow discharge,” made up of electrons and chrome and gas ions in a high energy state. (The glow is caused by the ions relaxing to a lower energy state and emitting energy in the form of light.) The atoms released from the target are attracted to the lower energy substrate and condense on its surface atom by atom until the desired thickness level is achieved. The magnetron also establishes magnetic fields that trap secondary electrons that were ejected from the target and keep them near the target to enhance ionization and generate a higher density of ions. With a higher density, deposition rates improve as the gaseous cloud condenses on the substrate.

Enlarge this picture A comparison between the steps used in American Trim’s PVD process vs. typical electroplating process.

This process is continued for each layer applied. For instance, Goodrich Technology deposits a layer of nickel chrome first, and then a layer of chrome. The thicknesses of the two layers averages around 1,500 angstroms, but can range in thickness on a part depending on whether it is a 3D part because PVD is basically a line of sight process. The surface directly facing the target will receive the most metal. While theoretically, only the substrate facing the target would receive the materials, in reality other surfaces will receive some coating as the metal atoms are bounced off of each other and the other ions in the glow discharge.

The PVD process allows for a durable end product. Colahan says that in his in-housing testing, the PVD coated parts were scribe marked down to the base substrate prior to testing. By doing this, each layer is tested, as well as the entire layer structure. So far, the process has been able to withstand the tests. For instance, Colahan says that one part was scribed marked and then subjected to more than 1,000 hours in a salt spray test. This far exceeds most requirements. In fact, a traditional chrome-plated part would only have to undergo 66 hours of testing, without a scribe mark, and most chrome today has a difficult time doing that, Colahan says.

The final step of the process is to apply a clear topcoat, which is typically an acrylic. This coating is used to protect the chrome layer and can be tuned to the appropriate application and give it properties for that use. The acrylic coat often used isn’t as resistant to showing scratches as say molded in plastic, however, but various top coats can be used to meet specific requirements for greater resistance. For automobile wheels, Colahan says they use a powder with good impact and UV resistance, but it does not have as good of scratch resistance as traditional chrome. For more scratch resistance, a harder coatings material can be used, but impact resistance can be sacrificed, he says.

Fluorex bright film comes in roll form. Soliant

Decorative laminate films also use a clear topcoat for protection. The films come in laminate form, sandwiching a thin coat of chrome metal between the clear coat and a substrate layer that contacts the component being fabricated. The films are especially appropriate for 3D parts as they can be stretched around a contour or other dimensional feature.

Some films feature a metal layer that is so thin, that manufacturers can print on the backside of the film and backlight the decorative piece for use as a nameplate. By day, as light strikes it, the decorative part looks like chrome, but when the light level drops, it shines with the printed image when the backlight shines through.

Two companies offering this technology include Sheffield Plastics, Sheffield, Mass., a subsidiary of Bayer MaterialScience, and Soliant LLC, Lancaster, S.C.

Chrome gives this cell phone a distinctive look. The material was sputtered onto the part by Goodrich Technology.

Sheffield’s recently introduced Makrofol 3D Metallic FG film that comes in either bright or low-luster matte. The top surface is a polycarbonate that offers increase scratched resistance, says Ted Trautman, principal product and process technologist at Sheffield Plastics. It is available in thicknesses of 0.008 in. or 0.013 in and can be formed in a high-pressure forming (HPF) process.

Bayer’s film is typically applied through a film-insert molding (FIM) process. The FIM process takes decorated film formed into the shape of the part by a combination of pressure and low heat. After the high pressure forming, the formed film can be placed into an injection molding machine and resin shot behind or over it. Trautman says while every application should be tested, in their own in-house testing they have been able to stretch the film over the form by 100 percent.

Soliant offers its Fluorex bright film, which won an emerging technology award from the Plastics Environmental Division of the Society of Plastics Engineers at its 2008 Global Plastics Environmental Conference (GPEC). The company also won the award in 2006 for its Fluorex paintfilms, which also can be used to decorate parts in chrome. Its use has primarily been in the automotive industry for bumpers and other parts, but a number of appliance manufacturers have adopted the process for nameplates, badges, moldings, and other decorative pieces. Its client list includes Siemens Home Appliances, based in California, and The Netherlands-based Royal Philips Electronics. Philips used it for a shaver that utilized colored chrome films. Because of the film’s translucency, they were able to backlight certain indicators such as the shaver’s battery charge levels. Previously, Philips had to cut out the sections where light was coming through in a secondary machining operation.

Ampacet offers a masterbatch that allows plastic parts to be injection molded to achieve a chrome appearance.

Soliant’s Fluorex bright films come in traditional chrome, matte, satin, color, and brushed chromes. The topcoat of the film can be custom formulated to offer increased scratch resistance and other improved mechanical properties. The film consists of a fluoropolymer-based clear coat, a metal layer, and an adhesive layer that can be bonded to a thermoformable ABS, PC, PVC, or TPO backing sheet. The film laminate is designed for use in low-stretch applications. Stretching it beyond about 40 percent can cause the film to distort and change color. On a steep 3D part, such as a button on a cell phone, this would translate to a maximum stretch of about a centimeter.

Soliant’s films are adhered to the substrate in a number of ways. It can come in the form of a decal in a post-part processing operation. Typically, however, it is processed with thermoforming, extrusion, or molding equipment. When thermoformed, the film is heated to about 300 DegC to become pliable, but not molten. It is then placed over a mold and drawn down by vacuum into the shape of the desired part. It can be thermoformed with vacuum, heat and vacuum, or with high pressure forming, which Pieter van der Ster, business director for The Netherlands-based Soliant says offers the best way to register the graphics. This is important if using the bright film with graphics such as a numeric keypad on a mobile phone.

The films can also be insert injection molded. In this method, the film is thermoformed and the preformed film is trimmed to fit into the mold tool cavity. The thermoformed inserts are placed into the injection-molding machine and the plastic resin is shot around it. Once ejected, the part is essentially in finished form, with little or no secondary processing required, van der Ster says.

The Philips shaver uses decorative film laminates that are backlit to reveal indicators such as battery charge levels. The Fluorex bright film from Soliant allowed Philips to reduce secondary machining operations.

To decorative a profile with chrome strips, extrusion lamination is the preferred choice, says van der Ster. In this method, the film is adhered to the substrate as it exits the die in an extrusion process, laminating them together.

One advantage of using decorative laminate films is that it allows for multiple film pieces to be used simultaneously. Currently, Soliant is working on a project that uses six pieces of film on one component. Compare this to the electroplating process in which the decorative part is separately chrome plated, and then later mounted to the main assembly.

For parts made solely of plastics, a third alternative is to use a resin masterbatch from Ampacet, Tarrytown, N.Y. The internal coloring approach for plastics offers the ability to produce parts quickly and with less part assembly required, says Doug Brownfield, strategic business manager for Ampacet. Instead of having to chrome plate a decorative element and then mount it to another part, the injection molding process allows it to be molded as one piece.

The chrome look on this wheelchair part is achieved by Goodrich Technology without the environmental issues associated with electroplating.

Ampacet’s product is called LiquidMetal and includes the raw pigments, resins, and additives that have been compounded into dry pellet form. The pellets can be compounded in a variety of resins including polypropylene, polycarbonate, polyamide, ABS, polystyrene, and polyethylene. The resins can be used with injection molding and extrusion technology.

A product within the LiquidMetal line is Bright Chrome for plastics, which can be custom formulated with a variety of colors and textures such bright chrome, matte chrome, red chrome, yellow chrome, brushed chrome, and other finishes. And, unlike electroplated chrome, or other surface treatments, the chrome look permeates throughout the part so that if it is scratched the succeeding layer looks the same. Additionally, the masterbatch can include additives for improved UV protection, flame retardance, and other mechanical and functional properties.

The gloss level can vary depending on the polymer chosen, says Brownfield. If using a PC or PET, the substrate will give a highly reflective surface that is similar to a chrome plated part. Polymers that are not as inherently glossy, such as ABS, PP or PE, will not have the same gloss levels. A highly polished tool or dye can also accentuate the gloss levels.

“I don’t know if you can ever duplicate the electroplated look, but this is a way to mold it into the part right in with the resins and the part is done. Little to no secondary operations are required, the number of parts can be reduced, and the manufacturer is not dealing with the disposal and ventilation issues that you have with electroplating,” he says. “If you want a more economical way to get a chrome part, this is a good option.”

Whatever method used, trade-offs are going to be made. Moving from electroplating chromium alleviated some health and environmental concerns but raised concerns about the quality of the coating. Molded-in plastics are easy to use, and inexpensive, but up close may look and feel more like plastic. Films and PVD processes are more expensive than molded-in plastics, but offer fast cycle times and a high-quality look at far less than the cost of traditional electroplating.

Aesthetic, cost, and performance requirements will determine the optimal method for a given application, but the important point is that designers now have more choices available for achieving the bright, shiny look of chrome.

For more information, email: American Trim, jswigard@amtrim.com
Ampacet, Eileen.Ferguson@ampacet.com
DuPont Powder Coatings, owen.h.decker@usa.dupont.com
Goodrich Technology, pcolahan@goodrichtechnology.com
Sheffield Plastics, info@bayerfilms.com
Soliant, pvanderster@PAINTFILM.com