Electroless Nickel Bath Ensures High-Quality Parts

Article From: Products Finishing,

Posted on: 2/1/1998

A new bath, multiple plating tanks and the elimination of chromates, fluorides and cyanides have helped increase quality...

Bernie Zapatha, owner and president of Poly Coatings, Sarasota, Florida, has four rules for operating a successful and profitable operation: Don't learn the tricks of the trade, learn the trade; Forget creative plating, do the system; EPA and platers want the same thing, an environment we can live in; and Quality, quality, quality.

Poly Coatings is a family business that specializes in electroless nickel, Poly-Ond and electrodeposited (sulfamate) nickel plating. Poly-Ond is a Teflon-impregnated electroless nickel plating used in plastic molds for dry lubricity. Mr. Zapatha's two sons and daughter manage production, quality assurance and customer service.

The company plates a variety of items for many industries, including firing devices for Patriot missiles and airbags, molds for injection and blow molding, wear components for sealing devices and other small, high-value components.

Poly Coatings has succeeded by establishing itself in several specialized niches, such as high-quality electroless nickel applied in thicknesses from 0.000050 to 0.005 inch, depending on customer requirements. The bath chemistry Poly Coatings has used for more than a decade is Nitec 75, a high-speed mid-phosphorus product manufactured by Heatbath Corp., Springfield, Massachusetts.

The bath is one of a family of electroless nickel products that also includes high-phosphorus and low-phosphorus baths. The high-phosphorus bath provides more than 1,000 hours of salt spray protection and is ideal for applications where both high corrosion resistance and high surface ductility are required. The thin plate uniformly deposits on steel and stainless steel, aluminum, copper alloys, titanium, magnesium and beryllium. The low-phosphorus bath is a mil spec product that produces a semi-bright finish on substrates ranging from steel alloys to ceramics.

Poly Coatings chose the bath because it had several years of success with the product at a sister plant, Poly Plating in Chicopee, Massachusetts. The product produces bright, high-quality deposits at a relatively low cost and offers high batch-to-batch repeatability. Because the bath provides excellent stability, it is also highly resistant to plate-out.

The bath is highly consistent and easily controlled via simple manual titration. The product maintains its brightness over multiple replenishments, a feature that minimizes both chemical consumption and waste.

Mr. Zapatha stated, "I've worked with, never in opposition to, EPA for 17 years. Our push-pull air system operates with two fume scrubbers, which eliminate odors and particulates. This gives us the best working conditions, as well as pollution control. Rinse waters do not leave the plant. The system is 100 pct closed loop. The only waste we generate is solids, which we dispose of in 55-gal drums. Our objective was to be a non-permitted facility, and that is what we have achieved."

Mr. Zapatha bought the business in 1985. The company's original offerings included decorative nickel and chromium and barrel plated nickel. The Zapathas changed this over time, installing systems for Poly-Ond, high-quality electroless nickel and sulfamate nickel. The elimination of chromates, fluorides and cyanides made the task of compliance simpler.

Choosing vendors carefully and making good housekeeping a priority eliminated many of the operational problems common to plating. One of the biggest problems was bath impurities, which caused deterioration of the electroless nickel bath. Organic contaminants result from drag-in of the cleaner, and acids are brought into the bath by the parts. Plus, cleaner or acid will be cupped in parts. "If ever there was a process that demanded love and care, electroless nickel is it. Our methods and policies provide that," said Mr. Zapatha.

Poly Coatings employs a similar process cycle for heat-treated, cold-rolled and stainless steels. Soak cleaning, rather than conventional degreasing, is used to preclean parts for 15 to 20 minutes at 168 to 175F. Two to four cycles of periodic reverse at 100 to 110F create a scrubbing action. With the proper cycle settings, the resultant hydrogen and oxygen bubbles dislodge the oxides. Dilute hydrochloric acid is used as a neutralizer. Then the parts are sent through the nickel strike/nickel chloride bath. The water rinses between stages are at ambient temperature and cleaned by electrodialysis. The bath can run at 185 to 195F, with dwell times dependent on pH and hypophosphite levels.

"We use the best available pH and automatic level controls to keep our bath performing consistently." Escalating costs and difficulties with bath consistency persuaded Mr. Zapatha to consider other suppliers. "We found this bath to be the best combination of consistent performance and reasonable price," said Mr. Zapatha.

Mr. Zapatha's son Glenn manages quality control. The activity of the bath is based on titration analysis of nickel metal and sodium hypophosphite, along with temperature and pH control. Glenn is responsible for the overall plating quality, although he is quick to emphasize that one cannot inspect quality into plating. "Everyone along the line has to be quality conscious," he said.

Poly Coatings has several other rules for maintaining maximum quality. Tanks are manufactured from sheets of polypropylene and are free of interior welds. The company never plates in the same tanks two days in a row. To apply a heavy nickel plate successfully, the baths must be spotlessly clean. Thus, at the end of each workday, workers filter and pump the chemicals to an adjacent tank and clean the one that has been used.

The following morning, a 50 pct nitric acid solution is used to passivate the tanks and heaters and dissolve the contaminants. The nitric acid is removed in about five hours, and the tank is again ready for service.

Poly Coatings has just 12 employees. "The average length of employment here is 10 years plus, and all of that experience comes from right here. We have rewritten ideas about employee involvement, reworked quality assurance and reinvented plating as we knew it," said Mr. Zapatha.

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