TPT September 2011

T echnology U pdate

Alternative powder coating systems

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

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: www.coatingsolutions.dupont.com Rippert GmbH & Co KG – Germany

The two-layer coating consists of an epoxy powder lacquer base coat and a polyester structure powder lacquer top coat

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

Fax: +49 5245 901 234 Email: info@rippert.de Website: www.rippert.de

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S eptember 2011

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