Evonik Degussa’s fluidized-bed coatings for wires and small tubes, such as those found in dishwasher components, offer nearly 100% material utilization.
More color is coming to the kitchen.
“Right now the stainless-steel look is popular, but Whirlpool and Kenmore have become very progressive with washer and dryer colors like Pacific blue, champagne, and black,” says Jeff Wright, North America sales manager of the porcelain enamel division of Ferro Corp. (Cleveland, OH, U.S.). “That’s been a surprise to me. The problem is the dark colors tend to show fingerprints.”
What’s driving consumer demand for more color? “Marketing,” says Ken Kreeger, director of business development worldwide for finishing equipment supplier Nordson Corp. (Amherst, OH, U.S.). “Marketing for stainless steel was big; now it’s color. It’s probably being introduced with washers and dryers because the kitchen has more appliances that have to be matched—the refrigerator, stove, dishwasher, and microwave.”
He’s glad to see the wide choice of colors and metallic finishes. “Painting costs will be higher, but the result will be a high-quality, automotive-type finish.” He adds that porcelain enamel (PE) still gives the highest-end finish but may lack the flexibility of different colors that powder paint can offer. “That’s something the PE industry is working toward.”
Metallic looks are still in vogue, and some appliance manufacturers have used laminates for many years to address the issue of fingerprints on stainless-steel refrigerators. That solution is being extended to other appliances, says Michael Jacobs, president of Horizon Business Group (HBG), in Northbrook, IL, U.S. “There’s a tremendous push toward using multifunctional coatings on both stainless steel and galvanized steel, as well as some other specialty metals, to address the issue of fingerprints across an entire family of appliances.”
Quick Color Changeover for Powder
Now the trend toward a richer palette of colors is driving OEMs’ demand for quick color changeover. Suppliers are positioned to respond. “In the past, a typical powder line would change colors in either a two-booth system or take 45–60 minutes in a one-booth system,” says Kreeger. “Now we have systems that take just 10 minutes or 20 seconds, depending on whether powder is recycled. Our Color Change Calculator will help show the manufacturer which direction to take.”
Fluidized-bed coating is used by Evonik Degussa GmbH (Marl, Germany) on wires and small tubes such as those found in dishwasher baskets, evaporators, and shelves. It has the advantage of nearly 100% utilization, says Holger Renners in customer service management. “The ease of changing colors is a big advantage of the fluidized-bed process. Most of the coaters use different colors for different companies and brands. So they have several powder tanks with different colors or powder grades in use.”
For wire coatings, Renners says the appliance industry mainly uses the fluidized-bed coating process. It’s used for dishwasher baskets, evaporators for freezers, and wire shelves for refrigerators and freezers. “Its advantages include high coating thickness, usually 400 µm, no loss of powder from overspray, easy change of colors, continuous coating ability, and high color variety. The disadvantages are facility costs, namely the oven, and the limited shapes and forms that can be coated.”
Renners provides a laundry list of changes in finishing technologies and materials that have been implemented in the last two to three years: higher-energy-efficiency production, increased coating speed, more homogeneous coating thickness due to better temperature regulation, color variety, improved mechanical properties such as elasticity, and reduced coating defects.
Porcelain enamel, such as the finish from Ferro Corp. on this outdoor grill, mimics metals and offers the advantages of durability, resistance to scratching and fingerprints, and ease of cleaning.
Getting the Waste Out
Renners says with Evonik Degussa’s Vestosint PA 12 powders designed for fluidized-bed coating and other processes, there is no waste, for example, from overspray. The coating on wire, such as that used for dishwasher baskets, is said to be tough; resistant to grease, oil, water, alkalis, saline solutions, and many organic solvents; and resistant to cracking even when exposed to chemicals. It can also dampen noise and vibration.
HBG has another approach to getting waste out of finishing lines. “Reducing the amount of unused and uncollected material is very important to our appliance customers,” says Jacobs. “To help them maximize efficiencies, we provide easy-to-understand application guides that are tailored to the equipment operators at the manufacturing facilities. We also provide hands-on technical assistance and analysis to our customers.”
Henkel (Düsseldorf, Germany) provides cleaning, pretreatment, and adhesive products that are applied to parts before they reach the paint shop. “These products are compatible with all commonly used powder and wet paint systems and can be used with existing equipment with only minimal modifications,” says Mike Perkins, appliance industry manager of Henkel Corp. “Specifically, our Bonderite NT-1, a wafer-thin coating, eliminates heavy metals and phosphates, reduces equipment contamination, and lowers energy consumption. (See “Pretreating with Nanotechnology,” Appliance, September 2007.)
“To offer color choices, manufacturers strive to go lean, even though the appliance industry hasn’t accepted it completely,” Kreeger tells APPLIANCE magazine. “In the past they had to have a large inventory, but the newer systems allow color changes faster so they can move toward a leaner operation and do so without hurting production.”
Launched in September, Nordson’s nVision Color Change Calculator is an interactive computer-modeling tool that enables a manufacturer to determine the effect of any variable on profitability. “Detailed ‘what-if’ scenarios allow input of 30 separate variables, such as the number of color changes, flow rate, number of guns, cost per hour to shut down a line, etc., to help users make educated decisions,” says Kreeger.
Henkel has been working on an alternative to iron and zinc phosphate processes for pretreatment of metal. Perkins says the prevailing industrial standard for about a century has been five- and seven-stage washers for metal pretreatment for iron and zinc phosphate coatings.
“While iron and zinc phosphate processes have proven to offer good performance, the process is time-consuming and conducted at elevated temperatures. The effluent is known to be high in phosphorus, a common nutrient that helps to sustain plant growth but, in extreme levels, can be detrimental to the ecosystem by creating an environment that encourages excessive algae growth in lakes and rivers. Some effluent remains in processing tanks as a phosphorus sludge that requires frequent tank maintenance for cleaning and removal. The process effluent also needs to be treated prior to release.”
Bonderite NT-1, Henkel’s nanotechnology-based conversion coating introduced in 2004, is a four-stage process that uses no regulated heavy metals, contains no organic components, and runs at ambient temperature. This alternative pretreatment process is environmentally friendly and energy-efficient. “The product generates minimum, if any, sludge, so maintenance is easy and relatively infrequent, reducing operating costs for the appliance manufacturer,” says Perkins.
This process has been adopted in some refrigeration, dishwashing, cooking, and laundry segments of the appliance industry to replace iron phosphating and, in certain cases, zinc phosphating. “We are working with appliance manufacturers to develop new products that will meet all of the performance specifications of those applications that require a zinc phosphate coating,” Perkins says.
What’s ahead for the appliance industry? Bundled features. Along with the demand for unique colors and metallic looks, appliance manufacturers seem to want other features already wrapped in as well.
Henkel is working with appliance customers to develop next-generation, process-friendly materials to replace the traditional zinc phosphate process. The materials are derived from formulations the company originally developed for use as pretreatment processes for the automotive industry, where extremely harsh environmental conditions are seen in day-to-day use. These pretreatment processes are being specifically adapted to suit the needs of the appliance industry.
Renners says appliance OEMs will demand newer and more brilliant metallic effects; reduced coating thickness—from 400 to 300 µm—for special applications; and new mechanical, thermal, and chemical properties that will require modifying or developing new polymer coating powders. “OEMs also seek optimizing of the mechanical properties, for example, elasticity and abrasion resistance, better corrosion resistance, and new colors, especially metallic effects.”
“Enhanced finish quality now appears to align with unique finish properties,” says HBG’s Jacobs. “Our customers want the visible parts on their products to look good and solve problems, whether it be an aesthetic issue like fingerprints or a physical issue like odors. To achieve this, our appliance customers now demand bundled properties, like fingerprint resistance, antimicrobial protection, and ease of cleaning, in a system that fits into their existing manufacturing process without additional steps. Our research shows that consumers are willing to pay a significant premium for an additional level of antimicrobial protection.”
MetoKote offers a coating application model that requires no capital investment by the customer for on-site installation and long-term operation of a customized, state-of-the art coating system. The InSite concept allows the customer to preserve capital for other manufacturing even as it controls costs in the form of a guaranteed price for the life of the contract. The company already manages approximately 150 paint systems.
Porcelain’s Staying Power
Porcelain was once the dominant finishing material in appliances, and still can’t be beat for temperature resistance.
In the past, “Manufacturing inefficiencies have driven appliance OEMs away from color,” says Cullen Hackler, executive vice president of the Porcelain Enamel Institute (PEI; Norcross, GA, U.S.). “I’ve given presentations called ‘Leveraging the Value of Porcelain Enamel,’ but it’s been difficult to get the Whirlpools of the world interested in color since the 1950s or 1960s.”
PE processing has become more efficient, and an important technological advance was recently presented at the PEI Technical Forum in Indianapolis, IN. In September, Mike Horton of KMI Systems Inc. (Crystal Lake, IL, U.S.) presented a paper on running the coating operation on one chain—the washer, coating operation, and furnace—with no transfers in between.
“It takes a lot of the cost out,” notes Hackler. “A couple of lines are in place, and we’re trying to get more people interested, but with consolidation in the appliance world, most folks are not building new PE lines,” says Hackler. “Sooner or later they’re going to have to.” He says when that happens, PE will be competitive on price with other materials, the cost difference between powder paint and PE being 1–2 cents per sq ft.
Ferro has launched three new porcelain enamel products: RealEase, AquaRealEase, and Evolution. “RealEase is a PE hybrid that competes with PTFE or Silverstone and is targeted toward cookware, griddles for stovetops, toaster ovens, microwaves, tabletop cookers, and grills,” says Wright. “It’s not recommended for oven interiors where temperatures could exceed 500°F.”
Metal utensils won’t scratch surfaces coated with RealEase, and colors won’t degrade with heat. The coatings, suitable for consumer and commercial appliances, are offered in a wide range of colors including sparkle effects. AquaRealEase is an innovative coating that could make costly self-cleaning ovens that operate at up to 1000°F (538°C) obsolete. It’s designed to provide an easy-to-clean surface on oven interiors. “It cleans with steam,” says Wright. “Put a pan of water on the bottom oven rack, set the oven at 350° for a half-hour, and clean with a damp sponge.”
Evolution answers consumer demand for trendy metallic finishes that resist scratching and fingerprints and are easy to clean. It provides a cost-effective alternative to stainless steel and copper in kitchen and laundry appliances, outdoor grills, and other applications. It has the advantages of PE that include durability, resistance to heat and flames, ease of cleaning, and color retention.
“Whirlpool in Mexico is producing appliances with Evolution coatings which they call Metallica, and we’re working with Weber Stephens on a grill,” says Wright. “In the sunlight the metal flake–type finish glistens.” He adds that the high cost of nickel, the main ingredient in stainless steel, is one factor driving the development of Evolution. “Evolution has the look of stainless steel but not the cost.”
PE isn’t just for high-end appliances anymore as the cost gap between PE and powder paint is closing. “We’re hearing from manufacturers that use both powder paint and PE that today it’s pretty much a wash,” says Wright. “It’s due to the improved processing efficiencies of PE and the increasing cost of powder paint materials which are petrochemical based.”
Two PE trends are making coating operations and material utilization more cost-effective, says Wright. “There’s a shift from spraying of wet enamels. More manufacturers are moving in the direction of electrostatic powder to streamline the process and cut waste. With spraying of wet enamels, they used to say one-third went on the part, one-third down the drain, and one-third up the dust collector. With electrostatic PE powder, there’s about 98–99% utilization. What doesn’t go on the part goes into the booth and is recirculated.”
A second trend is “two coat, one fire.” “Instead of applying a base coat, firing, then applying the color coat and firing, most people now apply a very thin adhesion-promoting base layer and then the second booth applies the finish coat and it’s sent to the furnace just once.”
He says developing a lower-firing PE is a goal of the industry and would cut manufacturing costs both in terms of saving on fuel and furnace tooling. “The heavy tooling required for high-temperature furnaces is an expensive part of PE.”
Hackler says there’s very little waste in PE application, in part because parts that can’t be reworked can go back to steel scrap. “The steel and glass melt and the glass goes to a slag layer which floats on top of the molten steel.” He adds that other coatings are being made more efficient as well. “The overspray of powder coating is collected, and with flow coating, what doesn’t get applied gets recaptured.”
Throughout the appliance industry, the finishing equipment continues to get the waste out, while bringing more color in.
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