Automotive Industry Partners Collaborate to Cut Shock Tower Weight
Like the Tower of London, automotive shock towers are built to survive brutal conditions outside and maintain stability. Often referred to as the workhorse of a vehicle, this part of a vehicle’s suspension system keeps it supported and stable. It takes a great deal of load in harsh under-vehicle environment, while maintaining its structural integrity is crucial for passenger safety.
While shock towers are traditionally made of casted steel, automotive OEMs are now making the move to using thin-walled aluminum, magnesium or mixed metals in this critical suspension assembly as part of vehicle lightweighting initiatives to help meet the 2025 CAFE standards of 54.5 mpg.
In fact, IHS Markit Automotive predicts that after 2019 German luxury cars will completely abandon steel front shock towers in favor of aluminum.
An International Academia, Government and Private Sector Collaboration
A number of automotive industry organizations have been examining the use of alternate materials for shock tower applications, including the U.S. Automotive Materials Partnership (USAMP). It launched the “Magnesium Front End Research and Development Project” (MFERD) to develop enabling technologies for production of large, integrated front-end vehicle structures. Henkel solutions were used throughout the the project.
MFERD, with support of the U.S. Department of Energy, also included an international collaboration involving organizations in Canada and the People’s Republic of China.
One of the focus areas of MFERD was automotive shock towers. The study included test panels and two demonstration (non-production) shock tower structures – one with magnesium and aluminum and another with high-strength steel, magnesium and aluminum.
Henkel’s Role in the Study
Henkel was involved in the “Task 5” (Corrosion) and “Task 9” (Joining) parts of the study.
Task 5 Objectives (Corrosion)
The goal of “Task 5” was to assess the general durability of the automotive shock panels. After pretreating and coating, the structures were put through cyclic corrosion testing using standardized OEM procedures. Henkel and other study participants established pilot plants to provide “pilot scale” capability for cleaning, pretreatment and top-coating of magnesium-intensive substructures.
Henkel coatings used in the study included:
- BONDERITE M-NT 1820 – During part of Phase III, BONDERITE M-NT 1820 was used to coat aluminum component pieces including the shock tower. The pretreatment was applied before assembly and after.
- BONDERITE M-NT 5200 – Also used during part of Phase III, BONDERITE M-NT 5200 was used as a converstion coating for magnesium component pieces. The pretreatment was applied before assembly and after.
- BONDERITE EC² – Some versions of the AlumiPlate® coated rivets used in the study were coated using BONDERITE EC². Test results showed this combination to be the most insulating in preventing corrosion within the study.
- BONDERITE MgC – This electro-ceramic coating was used in Phase II of the study on magnesium surfaces. It showed excellent barrier properties on magnesium surfaces and resulted in excellent corrosion protection.
Task 9 Objectives (Joining)
The goal of “Task 9” was to evaluate the adhesive bonding process and performance for advanced magnesium and/or dissimilar materials, as well as performance when used in conjunction with a metal pretreatment. Test coupons were created in order to evaluate joining, corrosion and durability.
Henkel adhesives and sealants used in the study included:
- Teroson EP 5089 – This structural adhesive was used in the joint between all magnesium and steel used in the study. It was considered the preferred adhesive because of its outstanding isolation properties. Wrought aluminum used in the study required metal pretreatment before adhesive was applied in order to prevent a chemical reaction. However, when using TEROSON EP 5089, a pretreatment was not required on electrogalvanized steel.
- TEROSON PV 1097 – This paintable seam sealer was applied to painted joints and rivet caps of both the steel and aluminum shock tower versions on overlaps and joint areas. Its role is seal out water, dirt and fumes.
Working Together to Find Solutions
The industry as a whole is working together to develop lightweighting solutions through the use of alternate materials. By conducting studies like the MFERD project, automotive OEMs and suppliers will continue to learn more about:
- How these new materials will interact with each other.
- The lightweighting benefits that can be achieved (as well as any potential limitations).
Together the industry will continue to make strides towards lightweighting advancements.
For additional information on adhesives, surface treatment, sealants, and cleaning technologies to support manufacturing aluminum and mixed metal shock towers, visit Henkel’s Smart Chemistry Hub.