The rising mix of metal substrates, notably the lightweight construction material aluminum and also increasing volumes of zinc-magnesium materials are imposing new challenges on the pretreatment process. This is why industry has for quite some time been looking for possibilities of retaining the known benefits of the tried and tested zinc-phosphating technology while at the same time also meeting new market demands. Besides the substrate mix, demands also include ever more stringent environmental requirements, rising cost pressure and also compliance with specific quality standards and tests of the automotive manufacturers.
Customized pretreatment boosts production
The new Gardo®Flex system from Chemetall consists of a large number of high-performance modules around the zinc-phosphating technology. This state-of-the-art process combines the traditional benefits of a conventional zinc-phosphating with optimized process components and thus meets modern demands of the global automotive industry.
For every process step in zinc-phosphating, Chemetall offers adequate technologies that are coordinated to match each other – from cleaning and degreasing to activation and phosphating through to the last rinsing step. These modules are specifically combined to suit each individual production line. This allows increasing the process efficiency and raising the production yield. Modules are selected as a function of the substrate throughput, the plant technology available, local market conditions and legal regulations. Chemetall can thus define an optimal solution for each pretreatment process in cooperation with the customer.
Modules allow for process economics
With the new Gardo®Flex system, significant process cost economics can be achieved, for example by reducing the temperature down to 35 °C in the zinc-phosphating bath. Field experiences have shown that – depending on the throughput – energy costs in the six-digit range can be saved. All process elements are optimally aligned and together with a distinctly longer bath service life, meaning lower water consumption and smaller effluent volumes, contribute to the resource-saving aspect of this technology. The reduced coating weight and finer crystal formation on the metal surface require less replenishment solution and thus lead to a reduction in the chemicals consumption. To give customers further benefits with regard to bath service lifes and maintenance costs, Chemetall in addition also offers an effective, demulsifying operation of degreasing baths.
The Gardo®Flex technology can be used in existing plants and usually does not require any alterations of the plant. Expensive cooling for activation or rinsing baths to suppress the formation of a phosphate coating on aluminum substrates is no longer required as the aim is to generate thin coatings.
No limit for aluminum
For some years already, the lightweight material aluminum has been gaining ground in automotive manufacture. Up to 70 per cent are pretreated in the production plants of the automotive manufacturers – a fact that may lead to technically most demanding application when using conventional zinc-phosphating processes. Gardo®Flex, by contrast, is suited for multi-metal applications without limitations. This modern technology can be used for all standard metal materials used in the automotive industry. No limits exist for the throughput of aluminum substrates and even non-galvanized steel can be treated without any problem. The process thus offers high flexibility with regard to the utilization rate of the customer’s production plant.
On aluminium substrates Gardo®Flex ensures a reduced pickling loss on the metal surface. This significantly minimizes the consumption of fluoride-containing additives by up to 40 percent. Also the phosphate sludge volume is dramatically reduced, which leads to less maintenance work and less disposal costs.
Another benefit of the Gardo®Flex technology is the deposition of a uniform, thin phosphate coating on the aluminum substrate, regardless of the percentage of aluminium in a car body. This phosphate coating smoothens out minor irregularities from previous process steps and thereby supports an even deposition of the e-coat. As the formation of a phosphate coating on aluminium substrates is specifically desired, there is no need for expensive cooling of the activation or rinsing tanks. An additional passivation step is optional, but in most cases not required to fulfill automotive specifications.
With only a zirconium passivation on aluminium, surface defects resulting from car body construction or pressing, such as for example scrub marks, scratches or impressions from the vacuum cups of the robots, can lead to visible problems in the cataphoretic paint layer. As a consequence, extra sanding operations may be required. These inconveniences can be reduced with the Gardo®Flex technology.
GardoFlex for greater independence
The state-of-the-art Gardo®Flex technology suited for multi-metal application can be directly integrated into any production line. As a consequence, no cost-intensive alterations are required and the benefits of the new technology can be optimally adapted to each individual production line. Renowned car manufacturers worldwide already rely on this new zinc-phosphating technology from Chemetall because Gardo®Flex offers them unprecedented flexibility with regard to their production process and also to their substrate throughput – at a high quality and optimized process costs.
Chemetall, a division of Rockwood Holdings, Inc. (NYSE: ROC), is a leading global supplier of special chemicals with a focus on processes for the surface treatment of metals and plastics. Chemetall is headquartered in Frankfurt am Main, Germany, and comprises about 40 companies and 22 production sites worldwide. With 2,100 employees, the Group achieved sales of about 592 million Euro (2013). More at www.chemetall.com.