Zinc Plating + Powder = Functional Aesthetics

Posted on Wednesday, July 15, 2015

Some things just go together. Abbott and Costello, peanut butter and chocolate. In the finishing industry, the same can be said about zinc plating and powder coating.

Medina Powder Coating, located in northeastern Ohio, believes in the magic of a great combination. “We may be one of just a handful of custom coaters east of the Mississippi that can offer a combination of high quality plating and powder coating in one stop,” says Dave Beck, general manager of Medina Powder Coatings. This marriage of technology provides what Beck refers to as “the gold standard of performance.”

“We have tested parts to beyond 2,000 hours of salt spray without any significant sign of corrosion,” says Medina’s in-house chemist, Gary Mest. That kind of performance has attracted interest from a wide range of interested customers, including appliance manufacturers, automotive part suppliers, and makers of agricultural products and medical devices, he explains.

“Every business has a niche. Our business is knowing what combination to use,” says Mest. The company has 50 years of experience in plating with zinc, zinc iron and zinc nickel alloys, but the plating and powder coating combination offers far more than just functionality. “Customers get the best of both worlds—a highly corrosion-resistant finish in a wide selection of colors that give the part a beautiful cosmetic appearance,” adds Beck.

Started in 1962 by Jim Krejci, Sr., the facilities—which today make up several buildings—have expanded from plating to both batch and a high-speed powder coating as well as hydro dipping immersion graphics capabilities. In March 2013, the company launched Medina Powder Coatings, a sister company of Medina Plating. The two sit side-by-side in northeastern Ohio. “Our proprietary dual coating system used in the powder coating operation allows us to plate parts in zinc, zinc nickel or zinc iron and then take them directly over to our powder coating line,” says Shawn Ritchie, who purchased the company in 2001 from the Krejci family and is now the company’s president. “There aren’t many other shops that can do that, but we wanted to be able to provide this service for customers,” says Ritchie

A common theme throughout the Medina facilities is “do it right the first time.” For Ritchie, it is more than a catchy slogan. The company has invested more than $200,000 in advanced analytical tools, including atomic absorption spectroscopy and several high-end analytical x-ray fluorescence analyzers to assure firsttime quality. These high tech instruments provide a constant vigil over the process that is uncommon in the industry.

“I wanted to get the OEM certifications to show we could perform at a high level and to differentiate ourselves from others,” explains Ritchie. “Where other companies rely on simple periodic checks of their sprocess, such as manual titrations, we monitor the quality of our materials before, during and after application,” adds Mest. This constant attention to quality has led to ISO/TS 16949:2009 certification and Medina Plating being named an Atotech Automotive Applicator, one of the first Triple-A platers in the United States to receive that recognition

“In the spirit of offering customers the right combination, we also have choices when it comes to how and where to powder coat their parts,” explains Beck. The company operates both a flexible batch powder system for complex parts and lower volume projects and a newer, fully automated powder line for higher production jobs

Marrying Technologies

For the dual-coat process, parts are first pretreated using a heated chemical cleaner to remove any oil/ grease, and then immersing them in an acid bath to remove any remaining rust. The batch system offers both media blasting and chemical pretreatment. A large 24' x 12' x 12' Pauli Systems blast booth allows Medina to use sand, walnut shell and glass bead media to prepare the surface of a wide range of large and small parts. Chemical pretreatment includes heated chemical degreaser and zirconate applied using a multihead Reimers spray wand.

Parts are manually powder coated in a custom designed side-draft powder spray booth using Nordson Encore XL® application equipment. “We generally spray to waste on the batch system,” says Rob Eason, lead powder coating technician at Medina, “because the mix of colors and different part sizes makes it less practical and less cost effective to reclaim powder than on the automated line where we schedule longer production runs.”

To “get it right the first time,” Eason has been able to boost the first pass transfer efficiency using the programmable features of the Encore spray guns. Push-button selection lets the powder operator choose the most efficient settings for the wide range of parts and powders they apply. “We use a number of preset gun recipes that allow us to change application settings like flow rate and electrostatics on the fly,” says Eason, “so we can go from a setting that is optimized for metallic flake to one that works better on deep recessed parts.

Once powder coated, parts are moved either manually or by tow motor to a 23' x 10' x 10' gas-fired convection curing oven. The batch system equipment, including the powder booth and cure oven, were designed, built and installed by Eaton Fabricating Company, located in nearby Grafton, Ohio.

When Ritchie decided to expand the powder coating capabilities a couple of years later, he again turned to Eaton Fab to design an automated powder line with the latest process control technology. The new powder coating line is a perfect complement to the batch operation. The line features two enclosed track overhead conveyors. One track is for a powder coat only system, while the other track allows parts to be first e-coated and then powder coated. The large custom engineered e-coat system is just being installed and provides yet another process capability for Ritchie to offer beginning later this summer.

Parts on the automated paint line are initially pretreated in a seven-stage all-stainless steel power washer that provides multiple washes and rinses to remove any surface contaminants from the metal parts. Medina monitors critical aspects of the pretreatment process like the pH and conductivity of the chemistry continuously with sensors that provide data to the system controller. An automatic dispensing system replenishes chemicals as they are used. A 10-minute drying oven, followed by a forced-air cool down zone, ensure the parts are clean and dry before powder is applied. All of the ambient air is filtered to maintain cleanliness throughout the entire coating process.

Eaton Fabricating Company worked with company engineers to design a booth that offers flexibility for parts as tall as seven feet high and three and a half feet wide. The booth is exceptionally spacious and well lit to allow operators to inspect parts as they are powder coated and to touch up any light coverage if needed. Five reclaim modules and 70 powder pumps provide fast and efficient reclaim capability. Parts travel past two opposing programmable gun movers each equipped with six Encore LT® spray guns controlled by a touchscreen computer controller. The gun movers are mounted on programmable in-out positioners so that the target distance of the guns to the part can be controlled electronically.To supplement the reciprocating automatic spray guns, Medina has two manual spray systems available in the booth for reinforcement and touchup if needed. From a single touchscreen computer, the operators can select from an extensive menu of stored part recipes. Each recipe provides control over nearly every facet of the process to assure consistent, uniform quality. At the touch of a screen, operators can set parameters including the precise position and triggering of each spray gun, the powder flow rate, and electrostatic controls.

Powder coated parts are cured for about 20 minutes in a direct gas-fired convection oven designed for high efficiency and uniform cure profile. Process thermocouples throughout the ovens interior ensure uniform heating across the entire part. The oven is kept at a slightly positive pressure to prevent airborne particles from contaminating the freshly painted part surface as the powder cures.

“The ability to powder coat on either the flexible batch system, or the new high-volume automated line gives Medina Powder Coating us the ability to pick a solution that best matches up with our customer’s needs,” says Beck. “For many customers who need flexibility and have smaller volumes or very complex part styles, we can be more competitive with our batch processing line. But for jobs where either higher volume or part geometry make sense for us to automate the spray process we can fine tune the application using the (control) system.”

Beck and Ritchie are excited about their dual coatings capability and have been on a mission to spread the word about the powerful combination of zinc plating and powder coating. “But it requires some education and finding the right customer” says Beck. “This is a high-quality process that offers corrosion production nobody can touch. But that’s not for somebody who is just looking for an inexpensive coating to paint their part. We are focusing on markets like automotive and agricultural products where corrosion is a major concern, but applications are finding us from appliance, medical and other unexpected areas. For example, the manufacturer of outdoor safety devices is using the dual coat system because they make products that people’s lives depend on. So the fun part is that this technology is opening up doors that we didn’t even know existed.”

Paul Mills is a marketing and business development consultant to industry chemistry and equipment suppliers. He has been a writer for the powder coating industry since 1994. Paul can be reached at 440-570-5228 or via email at pmillsoh@aol.com.