Metal Worker Chooses Electrocoating for First Finishing System

Article From: Products Finishing, ,

Posted on: 8/1/1997

After 84 years in business, metal fabricator adds in-house painting...

More and more of its customers were asking for painted parts. So Bert R. Huncilman and Son, Inc. worked with contract coating shops to have its sheet and plate metal parts and fabrications coated. Some were painted, some powder coated, and some were electrocoated. It just depended on what the customer needed. Then the time came for Huncilman to get serious about painting these parts in-house.

The New Albany, Indiana, metal fabricating company, founded in 1913, is operated today by the fourth generation of Huncilmans, Gordon and Jeff, having been passed the baton by father Lynn in 1978 and 1980, respectively. The company's credo, "Provide the customer with quality products and service while always being aware of their needs," has been followed to the present. The "service" part of that credo had a lot to do with the Huncilman's getting into the finishing business. By painting in-house, the company could improve turn around times for its customers, delivering what they want when they need it. In a word: Service. Those customers represent industries such as heavy trucks, packaging machinery, materials handling equipment and commercial lawn mowers, to name a few.

The first step toward in-house painting was an analysis of the painting processes Huncilman's customers specified. Conducted by Greg Hardin, who now is Paint Systems Manager, the study looked at how many parts were being electrocoated by outside vendors. Greg also considered how many of the parts being powder coated could be electrocoated instead. The scales tipped to the side of electro-coating. Plans were made to install a state-of-the-art paint electrodeposition system.

"The first thing we did was form a team with our suppliers," Mark Bland, Corporate Director of Engineering said. "Bringing together the equipment manufacturer and pretreatment and paint suppliers from the outset was vital to the ultimate success of our new painting facility. There was a great pursuit of cooperation among all the parties involved," he added.

Today, Huncilman's $4,000,000 expansion includes a 73,000 sq ft building in a new industrial park at the outskirts of New Albany. The electrocoating facility occupies 25,000 sq ft. The balance of the well lighted, air-conditioned plant will eventually house metalworking operations that are outgrowing the three other plants in town.

The System. Major elements of the electrocoating system include a loading/unloading station, a nine-stage fiberglass pretreatment wash tunnel, a fiberglass-enclosed paint tank, fiberglass post rinse tunnel, floor-level dehydration oven and balcony-level, bottom entry bake oven. All of this is served by 1,200 ft of overhead conveyor. A state-of-the-art wastewater treatment system handles effluents from painting and pretreatment. Along with its air treatment system, the finishing system is virtually pollution free.

The system can process hot-rolled-, and cold-rolled- steel, as well as aluminum in a wide range of gauges and sizes. It can also process parts as large as four by three by eight ft or two by three by ten ft.

The electrocoating system was designed and built by George Koch Sons, Inc., Evansville, Indiana, almost a Huncilman neighbor. "Koch was called in on the project early enough to have input on the design of the building, an opportunity they don't often get," said Gordon Huncilman, President.

Pretreatment. After the parts are loaded, the conveyor takes them into the 142-ft-long pretreatment wash tunnel at eight fpm. A summary of the nine stages is presented in Table I. Using zinc phosphate was an important consideration. Previously, Huncilman's contract painting and powder coating sources offered only iron phosphate. Superior salt spray resistance provided by zinc phosphate permits Huncilman to furnish even higher quality painted components to its customers.

Electrocoating. Leaving the pretreatment machine, the conveyor makes two 90-deg turns before taking parts into the 45-ft-long electrocoat paint tank. Parts make live entry (power on) into the 10,300-gal tank. The tank contains PPG Industries' Powercron 790-534 black cathodic epoxy paint. It is described as a seventh generation material that is free of lead and HAPs (hazardous air pollutants). The normal coating deposition cycle is two minutes. The paint can be applied at thicknesses ranging from 0.8 mil to 1.2 mils, depending on the customer's requirements.

Post Rinse. After emerging from the paint tank, parts are rinsed with permeate from the ultrafilters in a first stage that goes back into the paint tank. This removes non-adhering paint and allows its reuse in the process. Three counterflowing permeate rinses and a deionized water rinse follow.

Dehydration and Cure. Following the post rinse stations, the conveyor takes parts to a floor-level dehydration oven where water is baked out of the fresh, uncured paint film. The cycle typically is 13 min at 250F.

The conveyor then turns and rises to the bottom-entry upper level curing oven. The parts make five passes in the oven which operates at 450F.

Environmentally Friendly. Air and water treatment systems keep Huncilman in compliance with all environmental regulations. Water leaving the plant for the municipal water treatment system meets or exceeds all government regulations including pH of 5-10, 1.0 ppm zinc (daily limit), 1.36 ppm copper (daily) and solids of 225 ppm.

Finish Quality. The finish Huncilman is providing to its customers features high hardness, excellent salt spray resistance (1,000 hrs) and other performance properties. These are summarized in Table II.

Like a Job Shop. Huncilman doesn't manufacture finished, assembled products. Rather it serves a number of diverse customers by fabricating and painting a wide range of steel sheet and plate components. Because of this, the new electrocoating facility is more like a job shop, not a captive shop that paints one product day in and day out.

It didn't take long for Huncilman to realize the efficiencies of electrocoating and a more dense line loading could, in effect, expand line capacity. Now Bert R. Huncilman and Son, Inc. is accepting outside coating work, expanding its business scope from just contract metalworking to metalworking and contract finishing.

TABLE I—Pretreatment Process

Stage Process Chemical Time Temperature
1 Preclean Parco 305 with potassium hydroxide 30 sec 135F
2 Clean Parco 305 60 sec 135F
3 Rinse Water 30 sec ambient
4 Condition Fixodine ZL 30 sec ambient
5 Zinc Phosphate Bonderite 1993 60 sec 125F
6 Rinse Water 30 sec ambient
7 Non-chrome Seal Parcolene 99A 30 sec ambient
8 Rinse Recirculated DI Water 30 sec ambient
9 Halo Rinse Fresh DI Water 8 sec ambient

TABLE II—Electrocoat Paint Film Properties

Property Test Method Performance
Gloss (60 deg) ASTM D523-89 65-85
Pencil Hardness ASTM D3363-92A 2H minimum
Direct Impact ASTM D2794 Pass 120 inch/lbs
Reverse Impact ASTM D2794 Pass 100 inch/lbs
Cross-Hatch Adhesion ASTM D3359-93 4B-5B
Humidity ASTM D2247-92 1000 hrs minimum
Water Immersion ASTM D870-92 240 hrs minimum
Gravelometer GM 9508P 6 minimum
Throwing Power GM 9535P 12-15 inches

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