High-performance for next-generation car bodies

Lightweighting, multi-metal compatibility, with a focus on aluminium substrates – how thin-film pretreatment technologies fulfill the requirements for NIO’s next generation of cars.

With its advanced thin-film Oxsilan® technology, the Surface Treatment global business unit of BASF’s coatings division operating under the Chemetall brand, ensures a perfect surface treatment and excellent finish for the innovative ES8 from NIO, a multinational electric vehicle company headquartered in China. Their high-performance electric SUV designed exclusively for the Chinese market is a seven-seater and uses a multi-metal pretreatment process from Chemetall. The technology is specifically customized to meet the production requirements of the ES8.

According to a report by Bloomberg New Energy Finance, worldwide sales of electrified vehicles and plug-in hybrids will rise to 11 million in 2025 compared to 1.1 million in 2017. The growth will be largely driven by strong demand from China. The demand for smart electrified vehicles is increasing. At the same time, OEMs are more and more focusing on the use lightweight materials in order to achieve a greater driving range for their vehicles.

Chemetall, with its long history of innovation and dedication to process improvement and sustainability, identified earlier on two major trends in the automotive OEM market, that now play a crucial part in vehicle manufacture today: lightweighting, and multi-metal compatibility, with a focus on aluminium substrates. So, Chemetall began developing a zinc phosphating alternative, a silane-based pretreatment which became Oxsilan. In terms of quality performance, it is comparable to a zinc phosphate coating, but in terms of its technical and economic feasibility, the new technology is more advanced. Almost 10 million cars on the road today have been treated with this environmentally-friendly thin-film pretreatment. Oxsilan is now a proven technology, used globally in over 40 vehicle production lines.

What is Oxsilan?

Chemetall has been able to provide NIO with a tailor-made pretreatment process to match the ES8’s lightweight aluminum body, designed to maximize the vehicle’s driving range. Oxsilan is a zirconium and silane based conversion treatment and was especially adapted to achieve the level of protection required for NIO’s pure aluminium car bodies. The process gives excellent corrosion protection to the aluminium surface and promotes adhesion for the E-coat. whilst at the same time also offering significant reductions in water consumption, effluent, and energy usage in comparison to traditional pretreatments.

The base materials for the Oxsilan technology are zirconium and silanes. In the manufacturing process the silanes are hydrolysed and converted to polysiloxanes, then during the coating process, the reactive silanol groups are chemically bonded to the metal surface as well as to the paint coating. Heat treatment, which follows the curing of a subsequent cathodic e-coat further cross-links the polysiloxanes creating a coating layer in the range of 100nm, thereby reducing the consumption of chemicals and pretreatment times while increasing productivity: improvements of up to 65% have been achieved in some cases.This thin layer is sufficient to achieve the same degree of corrosion protection as a zinc-phosphate coating which is ten times thicker. This has been proven in combination with many paint systems. The numerous functional groups present in the polysiloxanes contribute to the excellent level of paint adhesion achieved. Additionally, Oxsilan offers considerable potential for process optimisation. With the Oxsilan technology, Chemetall has developed a sustainable, efficient, and economic pretreatment portfolio that exceeds today’s customer demands and is in harmony with current industry trends.

BASF supplies NIO with tailor-made processes – also for coatings

Chemetall provides NIO with tailor-made processes to match the specific demands of each of their models. Besides the Oxsilan pretreatment process, Chemetall is also supplying to NIO the brand new Gardoclean® S5166. This cleaning technology is phosphate-free and therefore meets the local legal requirements in China, which includes a ban on the use of phosphate-containing materials. To support NIO in achieving their production target, a team of technical experts from Chemetall works closely with the Chinese company. The team is regularly checking the stability of the pretreatment and cleaning processes at NIO ES8’s manufacturing site in Hefei, China, to ensure the highest level of quality is maintained.

Besides Chemetall, the Coatings division of BASF is helping NIO to shape their new generation of smart electric cars in China. With its coatings solutions, BASF has helped to create an unforgettable look with unparalleled performance for the ES8. The SUV uses BASF’s waterborne coatings solutions for all coatings layers. “As a strategic partner, we collaborated with the NIO design team based in Germany throughout the design and development process for the ES8, as well as during the production development stage in China,” says Nils Lessmann, Vice President and General Manager of BASF Shanghai Coatings Co., Ltd. “Our global key account team structure enabled design support to be given directly by BASF’s Automotive Color Design team in Münster, Germany, followed by the transfer of this jointly developed approach to the local team in China for localization.”

Investments in China

In order to strengthen its position in China and to deliver the high level of service and quality solutions customers have come to expect from Chemetall, BASF has invested in a state-of-the-art surface treatment site for the Chemetall brand in Pinghu, China. “We are looking forward to serving our customers in China with outstanding products and services from a state-of-the-art surface treatment site in the Dushan Port Economic Development Zone of Pinghu,” says Jin Hui, General Manager Chemetall China.

BASF’s Coatings division has also frequently invested in China, especially in Shanghai, to further enhance its proximity to customers in the fastest growing region for automotive coatings. Examples are the first regional Automotive Application Center in Asia Pacific at the BASF Innovation Campus Shanghai as well as a world-scale production facility which supports the growing Chinese automotive industry.




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