Specialty Finishing Boosts Customer Satisfaction

By Jennifer Creighton and Jim Destefani from Products Finishing

Taken from the January, 2006 edition of Products Finishing.

Carefully chosen wet processes allow a mechanical finisher to add value…

Founded in 1961, Rapids Tumble Finish (Eaton Rapids, MI) began business by providing tumble finish services. The company later added vibratory processing for deburring, cleaning, burnishing, radiusing and finally in the late 1980’s media blasting services.

RTF’s only facility is in central lower Michigan. Its customer base is geographically widespread but heavily automotive. If you think this doesn’t sound like a strategey for success right now, think again. In April 2005, the company passed a notable milestone: not only did they post record sales, but did it so following 75 quarters of steady growth. Sales in this record month came from the same diverse sources as they always had: longstanding customers, new customers, OEMs, Tier 1s, job shops that RTF works with reciprocally and from across the Atlantic Ocean.

The company’s latest expansion of its capabilities involves two specialty finishing technologies, black oxide and zinc phosphate. RTF already has customers lined up for both processes…

President and Owner Loren Cowles believes that the factors that allowed his company to thrive as a supplier of surface enhancement will allow it to be equally successful with surface coating. Chief among those factors is a strongly proactive stance when it comes to quality of incoming parts.

“Quality really does begin before anything happens at all, not after processing or in-process,” Cowles says “Determining exactly what you’re receiving , including what’s on those components, is a policy commitment. It helps protect your chemistry, but more than that, it’s a big step toward getting the job right the first time.”

A related factor is quality certifications, Cowles believes. “ISO, QSB and other benchmarks give us credentials when we need them and the flexibility to choose work that best fits our capabilities,” he says.

Equipment is also important: RTF designs and builds most of its own, from inspection gages to loaders for wheelabrators to parts dumpers and rust inhibiting equipment. The company also operates its own fleet of trucks to more closely control deliveries.

Chemistry is critical, too. RTF processes ferrous and nonferrous products using the same steel or ceramic media, changing the liquid compound according to the process requirement. Often, RTF custom-blends compounds to achieve a more precise result.

Finally, there’s the factor of job mix. One ongoing program involves surface repair of high-value components produced in Europe. “Processing that requires us taking a 15 or 20 micro-finish down to 4 or 5 is an excellent fit for us,” explains Cowles. “We’re geared to a 0.0002 inch standard, and we can handle close tolerance. Our philosophy has been to focus on high-value parts-particularly ones with complex shapes-turn them around fast and build customer loyalty. Customers more often call on us to solve problems, such as dimensional repair or resurfacing of rusted parts made in Asia, than to just provide a service.”

This is particularly true with work Cowles describes as reverse process engineering. “It’s really vendor engineering, in that we spec to the OEMs, including one automaker, precisely how much material our surfacing will take off and therefore, what to send us in terms of product size. While this is not the norm, it has proven very effective in producing large volumes of parts that are exceptionally consistent in both dimensions and microfinish.”


The new zinc phosphate and black oxide line clearly creates opportunities to do more with parts that are already surfaced, a value-added service that Cowles believes will benefit customers in lower costs, better scheduling and reduced transportation. “We surveyed our service area and determined that zinc phosphate and black oxide were key,” he explains.

Black oxide finishing is not new, of course, and its applications in traditional markets-automotive, for example-are not necessarily expanding at this time. But it has gained a cost advantage over rival technologies, according to Cowles, who says his company had identified some non-traditional uses for black oxide coatings that can offer advantages for customers. “And of course, we like black oxide for the one thing that it does not do-and that is change parts dimensions,” he adds.

In considering black oxide and zinc phosphate chemistries, RTF looked for products with a performance history that would be stable, simple to operate and not create headaches with waste treatment. Cowles found that combination in a family of products manufactured by Heatbath Corporation, Indian Orchard, MA.

“The goal was to turn out a coated product that is as good and as consistent as our deburred ones,” Cowles explains. “Heatbath’s technical sales repetitive in this region had exactly the expertise we needed, not just with chemistry, but with equipment recommendations as well.”

Heatbath worked with RTF first to determine the size and scope of the equipment that would be needed. “A couple of the big equipment makers came off as rigid and not very good at listening,” Cowles recalls. “So, we considered numerous configurations and did our preliminary drawings. With their years of experience, Heatbath’s help was invaluable. We jointly decided on a layout featuring process lines and cleaning stages that allow parts headed for both the zinc phosphate or the black oxide process to be shared. The line was designed to accommodate a standard maximum barrel size. Parts arrive in standard tubs and one tub equals a barrel. So, when loads emerge, the tub is just refilled. Barrels are approximately 2,000 lb capacity, but there are exceptions – muffler caps being one – and the line has to be flexible enough to accommodate those.

The equipment was engineered to provide five major finishing options: acid pickle and rust preventative oil, black oxide, heavy zinc phosphate, black zinc phosphate and calcium modified zinc phosphate. It offers four options for topcoats:a waterdisplacing rust preventative oil for maximum corrosion protection, water-displacing rust preventative oil for dry-to-the-touch, water soluble rust preventative oil and water-based rust inhibitors.

The system offers the flexibility of rack or barrel parts processing; gas dryers are used for racked parts, barrel processed parts are dried in spin dryers. Barrels are designed to accommodate separation chambers that can empty independently, so two different parts can be run simultaneously.

The system will run standard and custom process cycles; chemical analysis and process control are computerized for ease of use and to provide process documentation. With each load, the line generates a process sheet indicating the process cycle used, the tank temperatures and relevant chemical parameters.

RTF’s selection of products was guided by factors that included cost, process repeatability, tech support and waste treatment. The U.S. Environmental Protection Agency’s Region 5, and Eaton County in particular, heavily regulate effluent containing strong alkalis, corrosive solids and oxidizing agents, and the costs of compliance can, make processes uncompetitive if products are not chosen carefully.


For the cleaner, RTF selected Heatbath’s Uni Kleen® 1293, a caustic, heavy-duty soak cleaner originally developed to eliminate solvent pre-cleaning in electrocoating operations. The product is effective for the complex shapes RTF often processes and quickly removes polishing, buffing and forming compounds.

The acid pickle stage uses Heatbath Rust Remover 4, a liquid acid pretreatment for pickling and decaling ferrous metals. It isused at ambient temperature and contains an inhibitor to prevent base metal attack where long immersion is needed to remove heavy scale, such as with the parts made in Asia.

For black oxide chemistry, RTF chose Heatbath’s Pentrate® Ultra L, a “deep black” formula that produces a minimal build-up of colloidal iron in the working bath to minimize the risk of superficial red, brown or green films. Of particular importance to RTF was the incorporation of a wetting agent, which greatly reduces chemical loss due to drag out and thus minimizing the costs of both product and waste treatment. RTF included automatic chemical feed and water additions for the black oxide tank.

On the zinc phosphate side, the Black Pre-Dip stage uses Phos Dip® BZP-4, a pre-phosphate coating, which can be followed by zinc or manganese phosphate. RTF will also provide manganese phosphate processing if customers request it.

The heavy (2,000 mg/sq ft) zinc phosphate chosen for the automotive, off-highway, machinery and other heavy-service components RTF processes is Phos Dip® 1263, aproduct with a high tolerance for iron in solution. This zinc phosphate produces high uniformity of parts coverage and minimal sludge formation in the working bath.

For microcrystalline zinc phosphating, RTF installed Phos Dip®R-2-LT, a calcium-modified zinc phosphate process that deposits a coating ideal for pre-paint.

One of several topcoat ooptions for use over zinc phosohate coatings is Heatbath Rust Inhibitor 1438, a nitrite-free, solvent-free water based product developed for in-plant rust protection of steel products.

Heatbath Lab Oil 100 is a water-soluble, emulsion-type rust preventative oil that provides high levels of corrosion protection, good emulsification characteristics and low toxicity. It is barium-free and dry to the touch when applied over heavy zinc phosphate.

Where maximum corrosion protection is needed, RTF chose a thin-film rust preventative, Heatbath Pen Dip® Super. Developed specifically for black oxide and phosphate-coated components, the solvent-based rust inhibiting oil has excellent water displacing properties. It can also be used to protect highly finished parts during manufacture.

The other water-displacing rust preventative oil selected by RTF is Pen Dip® A, which produces an extremely dry film and allows immediate shipping.

The first parts processed on the new RTF line were nuts, tubes and muffler caps. All met customer specifications for surface finish and for surface coating.

To read more about Rapids Tumble Finish’s new coating lines and the Heatbath® products chosen for their high quality black oxide and zinc phospate coatings, click the PDF icon below.

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