TPT September 2011

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78 September 2011 ›
Technology Update
IMPROVED performance, anti-corrosion
properties and better value: these were the
demands a manufacturer of transformer
stations placed on a new coating system.
They were realised in the form of a
powder coating system developed by
systems, chemicals and powder coatings
manufacturers working in close cooperation.
Elbag Energietechnik GmbH transformer
stations are used for feeding electricity
from renewable energy sources such as
photovoltaic plants and on- and offshore
wind farms into the medium voltage net, and
from there into the grid. These applications
can place extremely high demands on
the anti-corrosion properties of the metal
housings of the transformer stations.
As the existing liquid coating system was
no longer able to cope with the number of
housing parts to be processed, the company
decided to invest in a new coating system
in autumn 2008. The criteria for the new
system were that the coating process had
to be of extremely high quality, achieving
anti-corrosion class C5, and at the same
time more economical and environmentally
friendly. The company decided in favour
of a powder coating system from Rippert
Anlagentechnik GmbH & Co KG, pre-
treatment chemicals from Haug Chemie
GmbH, and the Alesta® powder coating
system from DuPont CoatingSolutions.
The system is partially automated and
features flexible transport facilities, a waste
water-free two-chamber pre-treatment plant,
a retained water dryer, an enclosed manual
powder coating cabin and an enamelling
furnace with a heat recycling system.
Rippert, Haug Chemie and DuPont
CoatingSolutions carried out a
comprehensive series of tests together to
bring the process up to Elbag’s required
anti-corrosion standards. The result
showed that a combination product with
multi-metal capabilities, comprising a
water-based acidic cleaning agent and iron
phosphate solution, provides an optimised
pre-treatment process for galvanised steel,
aluminium and black steel substrates.
Adhesion and anti-corrosion properties
as well as the outdoor properties of the used
liquid paints formed the basis for the choice
of the new powder coating system. Sample
sheets of the substrates used by Elbag
were coated in liquid paint and subjected
to corresponding tests to obtain exact
information about their properties.
DuPont CoatingSolutions developed two
different powder coating layered structures
based on the results:
1) Parts that are being used outdoors
under normal conditions are chemically
degreased and coated in iron phosphate,
undergo a two-step rinsing process with
deionised water, then receive one coat
of the weather-proof polyester structure
powder lacquer Alesta IP, series IE 0501.
2) Components that need to meet the
toughest anti-corrosion requirements (C5)
are pre-treated, then receive a base coat
of the epoxy powder lacquer Alesta E,
series EE 7002. The complete top coat
is lacquered with the polyester structure
powder lacquer Alesta IP.
Both layered structures were tested to
see if they met the customer’s criteria. The
two-layer coating did not show any signs of
creep corrosion, even after being sprayed
with salt water for 2,160 hours.
By using the powder coating that was
introduced in mid-2009, Elbag has managed
to improve the quality and environmental
properties of its products and has also
increased its capacities. Throughput times
(from hanging to taking down of the parts)
for one and two-layer coatings are 51
minutes and 78 minutes respectively.
Compared to throughput times for liquid
coatings, ranging from 210 to 300 minutes,
this means that performance has increased
by up to four times while requiring the same
number of employees.
The integrated heat recycling system,
energy-efficient drives and frequency
inverter-controlled powder cabin extractors
all contribute to the cost-effective operation
of the system.
DuPont CoatingSolutions – Germany
Website:
Rippert GmbH & Co KG – Germany
Fax: +49 5245 901 234
Email:
Website:
Alternative powder coating systems
The two-layer coating consists of an epoxy powder
lacquer base coat and a polyester structure powder
lacquer top coat