in Vol. 12 - November Issue - Year 2011
DuPont and Rippert powder coating systems are cost-saving alternative to liquid coating systems. Capacity And Quality Up, Costs Down
The part-automated powder coating system features a flexible transport facility with lifting and lowering stations and a waste water-free two-chamber pretreatment plant
The two-layer coating consists of an epoxy powder lacquer base coat and a polyester structure powder lacquer top coat and stands up to the toughest anti-corrosion requirements. Image source: Rippert
DuPont: DuPont develops and sells products and services. Since 1802, the company creates sustainable solutions for a better, safer and healthier world on a scientific basis. With a presence in over 70 countries, DuPont offers a broad range of innovative products and services to its customers for various markets including agriculture, food, construction, communication and transportation. DuPontTM, Alesta® and PercoTop® are trademarks. Rippert: Rippert GmbH & Co. KG is a family-owned SME in the plant construction sector. The company develops and produces innovative surface treatment systems with focus on lacquering and coating systems as well as industrial ventilators and filtering systems. For more than 40 years, the main facility in Herzebrock-Clarholz, Westphalia, has been producing sustainable and energetically optimised products. The company’s products are being used in numerous industries – from the furniture sector to plant construction, agriculture and wind power plants.
A much improved performance, excellent anti-corrosion properties and better economic value – these were the demands a leading 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. At times, these applications place extremely high demands on the anti-corrosive 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. After an intensive period of choosing between different systems, the company decided in favour of a powder coating system from Rippert Anlagentechnik GmbH & Co. KG, pretreatment chemicals from Haug Chemie GmbH, and the Alesta® powder coating system from DuPont CoatingSolutions.
Optimises processes through close cooperation
The system is partially automated and features flexible transport facilities, a waste water-free two-chamber pretreatment 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 Elba’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 pretreatment 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 pretreated, and 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.
Performance up to four times higher, costs lower
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 considerably. 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. Elbag also benefits from the powder coating process in terms of costs, providing the company with considerable savings. 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.
Similar appearance for liquid coatings
Elbag coats around 80 percent of all parts with powder. The remaining components are still being coated in liquid paint if customers have specific requirements such as the use of water-based lacquers or a three-layer coating structure or if housing parts are too large to fit in the powder coating system, which can only accommodate parts up to 3000 mm x 1200 mm x 2000 mm (width, depth, height) in size. In these cases, the liquid coating system PercoTop® from DuPont CoatingSolutions ensures that the optical and technical properties of liquid-coated parts match those of powder-coated components.