PF Online Feature Article - Low-Nickel Seal is Modern Solution

Low-Nickel Seal is Modern Solution

This mid-temperature low-nickel seal helped Modern Aluminum Finishing solve a number of problems...

By Ken Sigsbury
Modern Aluminum Finishing

Modern Aluminum Finishing is the largest job shop east of the Mississippi, with three plants in the United States. One is in North Adams, MA, (the original plant and headquarters), and two others are in Adel, Georgia, and Barnwell, South Carolina. In the summer of 2002, at the recently acquired Barnwell facility, we were having trouble producing a consistently high quality finished product. The finish we were working on was electrolytic bronze, and there were real problems with consistent color matching and uniformity. The chemical supplier at the South Carolina plant was unable to come up with a solution, so we asked Chris Ebbrecht of Clariant Pigments and Additives to send in a technical team to do an audit of the facility. With their help we were back in production in three days.

When the team from arrived at the facility, it took samples of the bath and set up an action plan to correct the problem. According to Mark Jozefowicz, technical manager for aluminum coatings at Clariant, “Our suggestions on reworking the electrical delivery system were acted upon, and they converted the chemistry in the bath to Sandocolor TSN. This is a one-component coloring chemistry, which provided Modern with a forgiving process that provided excellent color uniformity. The very first load processed was the best they had ever seen coming off that line. Since that first load, Modern’s Barnwell plant has been producing consistent high quality colored extrusions.”

The Basis for a Partnership
As large as we are, with 280 employees in three facilities, Modern is still the same family-owned and operated business that my father, Frank R. Sigsbury, started in 1959. We believe we have lasted this long in business because we have kept our focus on customer satisfaction. And although we are considered a large job shop operation that services major extruders throughout the United States, Canada and Mexico, we still cater to small companies in several industries. This means we need to work with organic dyes for color-anodized coatings for all types and sizes of parts, as well as inorganic pigments for bronze or black coatings commonly used in architectural applications.

As a result, we are constantly assessing the amount of chemicals we add to our baths to maintain quality and longevity, and to ensure color consistency in the finished coating. At the same time, we are cost conscious and environmentally conscious, so we are always trying to limit energy consumption and chemicals and look for ways to reduce the amount of waste we generate from our operations.

Next we tried a new chemical solution for color anodizing; a low nickel, mid-temperature seal that had proven to eliminate phosphate buildup in seal tanks. This experiment took place in our North Adams facility.

Successful Commercial Test
Our North Adams facility has a phosphate-containing chemical bright dip. Phosphates, like any chemical on an anodize line, are carried from tank to tank, and the buildup of phosphates eventually contaminates the seal. A contaminated seal requires the use of more chemicals, and this is costly and environmentally burdensome. The baths need to be changed more frequently, and since the baths contain nickel, which is preferred for color-anodized aluminum, federal, state and local governments regulate the wastes.

While most large job shops like ours might want to avoid using nickel in its chemical solutions, nickel has proven invaluable for bright color finishes. Nickel makes the sealing process more efficient, it helps stabilize the dye, and it improves color fastness in the finished product. But it has its drawbacks.

How the Mid-Temperature Low Nickel Seal Works

An anodized aluminum coating is composed of aluminum oxide that takes on the form of micro-capillaries, which extend from the base aluminum to the oxide surface. To seal the coating, these capillaries need to be plugged. At mid-temperature, this is accomplished by the combination of oxide hydration and chemical precipitation. In the case of Clariant’s Anodal Low Nickel Seal, it is believed that the specialized organic surfactant catalyses the hydration reaction and at the same time co-precipitates as a coordinated structure with the aluminum, the nickel, and the magnesium. The result is an effective seal that works within 10-15 min at a temperature of 170F. Simply filtering the seal will eliminate phosphate contaminants in the bulk solution. Phosphates are continually precipitated out of solution in the form of flocculated particles.

The new seal used more magnesium and less nickel (about one-tenth of the nickel required in conventional seals). In laboratory tests, the supplier had discovered that the chemistry in the seal could rid itself of phosphate ions through precipitation (and subsequent filtration) of particles composed of aluminum, nickel and a specialized organic surfactant. Other seals currently in use and tested under the same conditions did not show the same results. To validate performance, Clariant was seeking a commercial partner to do a test run.

We agreed to the commercial trial in the fall of 2002. After all, if it worked in our tanks as it did in the lab, we could extend the life of the seal, reduce our use of chemicals and hazardous waste, and achieve a better quality finish, which was, of course, our number one priority.

The trial run has transformed itself into a partnership. Our chemical costs are down, as is the environmental impact of our operations. Moreover, the quality of our finished products is great.

Today, we believe Modern Aluminum has a partnership that will continue to bring new chemical solutions to the commercial floor, which will help sustain not only our business but also the industry. There are no new players in the anodizing field, and we anticipate that very few will be starting up a business that requires such a high capital investment and stringent environmental controls. The future for those of us in this field lies in breakthroughs in chemistry and in partnerships that help solve real-world problems.