Both the rinse water and phosphating solution are
reused in a closed loop system, adding to the eco-friendly
process.
CORROSION TEST RESULTS
With the environmental-friendly thermal diffusion
process that supports the ELV Directives and the excellent performance provided by the duplex coating, the
Greenkote process is gaining recognition and acceptance
through a series of successful tests run by some of the
major automotive manufactures and Tier 1 suppliers.
In June 2003, VW qualified Greenkote PM coating with
e-coat topcoat for its TL-196 specification “Duplex
Coating for Small Parts” for corrosion protection. In July
2007, Audi approved Greenkote PM- 10 plus e-coat topcoat for its lock parts after passing the TL-196 specification of 60 cycles of corrosion testing.
An independent lab tested an automotive clamp to the
ASTM B117 neutral salt spray test. The clamp had
Greenkote PM- 10 zinc TD coating at 15 microns film
thickness and black e-coat at 18 microns film thickness,
for a combined total thickness of 33 microns (1.3 mils).
The final test report gave a ten rating for the scribe with
0.0 mm creepage and a rating of 10 for no surface defects
(see Figure 5 below).
Figure 5
Additional testing shows that Greenkote performs well
on fasteners as well as stamped parts. In 2006, PPG tested M6 and M8 fasteners using Greenkote PM Coating
with Powercron XP electrocoat and reported no red rust
after 960 hours of salt spray testing.
THE ADDED VALUE OF TD COATINGS
Greenkote PM coatings provide high performance corrosion protection at a competitive cost when compared to
other zinc coatings such as zinc plating, hot dip galvanizing and zinc metal flake coatings. With zinc TD coatings
there isn't any hydrogen embrittlement, which can be a
concern with electroplating.
Additionally, Greenkote PM coatings provide excellent
rubber to metal bonding surfaces, eliminate porosity in
sinter metals and produce a thin, uniform thickness on
threads, blind holes and even tube interior walls. They
also provide a hard, wear resistant surface. Wear testing
on striker wire loops showed normal wear and gouging
after 5000 cycles with another duplex coating, while the
Greenkote PM and e-coat barely showed any signs of
wear after 10,000 cycles.
As the automotive industry continues to seek out new
products and technology to stay abreast of the ever-tight-ening restrictions and regulations placed upon it,
Greenkote will continue to respond to stringent environmental standards by providing an eco-friendly alternative to traditional coatings.
With the opening of the Sauerlach facility in Germany,
the reach of the Greenkote thermal diffusion coatings
process is now more widespread than ever. As Audi and
its Tier 1 suppliers can attest, Greenkote PM zinc coatings can provide the corrosion protection for automotive
lock parts as a cost-effective solution for meeting envi-ronmental-based directives. CW
About the author:
Dan Riter is director of engineering at Greenkote Plc located
in Cleveland, OH. For more information on thermal diffusion coatings, contact Dan Riter at 440-243-2938 or
dan.riter@greenkote.com.
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