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
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
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
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
founder. "We believe that the electroless nickel forms a chemical
the aluminum, not just an interlocking of materials. Because of
there are no gaps between the wheel and the aluminum, which could
There are several layers of plating on each wheel. Electroless nickel
as the barrier coating. When wheels enter the shop they are lightly
to remove machining lines. After buffing, eight wheels are racked
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
employees can check the exact time and part position.
Parts go through a typical aluminum cleaning cycle: alkaline soak,
acid desmut and a double zincate. All solutions are monitored 24
hrs a day
in the facility's laboratory. The electroless nickel system has
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,"
Mr. Schardt. The auxiliary anodes provide the proper nickel and
thickness in holes and recesses.
On the second plating line, wheels are plated in a semi-bright and
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
Tom Geraghty, quality control manager, uses a Fischer Isoscope beta
backscatter instrument to check for plating thickness.