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  Dayton Alloy Wheel combines electroless nickel with a decorative finish for corrosion resistance and good looks...
By Beverly A. Graves, Editor

Winters in the Midwest and northeastern United States are tough
on automobiles, particularly the wheels. Not only do the wheels suffer
through ice and snow, but they contend with sand and salt. Because
of this, major automobile manufacturers have sought ways to improve
the corrosion resistance of wheels while maintaining their decorative
qualities. In 1990, General Motors approached Dayton Alloy Wheel,
Dayton, Ohio, and asked it to help with this predicament. For two years
Dayton Alloy Wheel worked with Enthone-OMI to develop a process
that would provide corrosion resistance as well as decorative qualities.
They found that 1/4 to 1/2 mil of electroless nickel under a decorative finish
provided the best protection over the entire aluminum wheel.

"You could apply decorative plating until it is quite thick and achieve the
corrosion resistance. But the weight of the wheel is higher than it is with
electroless nickel," stated Jim Schardt, Vice President and company
founder. "We believe that the electroless nickel forms a chemical bond with
the aluminum, not just an interlocking of materials. Because of this,
there are no gaps between the wheel and the aluminum, which could
cause peeling."

There are several layers of plating on each wheel. Electroless nickel acts
as the barrier coating. When wheels enter the shop they are lightly buffed
to remove machining lines. After buffing, eight wheels are racked on each
plating rack. Each wheel's position on the rack and the time of day it is
plated is carefully recorded. If there are problems with a certain wheel,
employees can check the exact time and part position.

Parts go through a typical aluminum cleaning cycle: alkaline soak, etch,
acid desmut and a double zincate. All solutions are monitored 24 hrs a day
in the facility's laboratory. The electroless nickel system has its own
controls for maintaining the solution. The nickel baths have automatic
brightener feeders and the other plating baths feature automatic

Following cleaning is electroless nickel plating and a copper plate.
Wheels are then removed from the rack and buffed. After buffing, wheels are reracked for decorative plating. "A key part of the entire wheel-plating
process is the auxiliary anodes used in decorative plating," noted
Mr. Schardt. The auxiliary anodes provide the proper nickel and chrome
thickness in holes and recesses.

On the second plating line, wheels are plated in a semi-bright and bright
nickel followed by microporous chromium.

Once the wheels are plated, rigorous testing begins. As wheels roll
off the line they are weighed as part of a thickness check. Following that,
Tom Geraghty, quality control manager, uses a Fischer Isoscope beta backscatter instrument to check for plating thickness.

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