Acura Adopts Aluminum-Steel System for Vehicle Doors

Honda Motor Co. says the North American version of its 2014 Acura RLX large luxury sedan will be the first to use a three-part system developed by the company to mass-produce doors with aluminum outer and steel inner panels.

The technique combines a two-fold hemming process with special adhesives and revised panel edge design. Honda says the three technologies address the two main challenges of fabricating components out of dissimilar metals: electrical corrosion and different rates of thermal deformation.

Steel-to-steel panels are joined by slipping the edge of one panel into a U-shaped flange in the second panel and spot welding the two together. Honda's aluminum-to-steel system substitutes a low-elasticity adhesive for the spot weld and a "3-D" double flange that allows the two metals to expand and contract at different rates.

The company says its system reduces door panel weight about 17% compared with an all-steel design. The configuration also shifts the door's center of gravity toward the centerline of the vehicle, which improves vehicle dynamics.

The $61,000 RLX goes on sale next month. Honda says it will eventually expand the new fabrication process to unspecified other models.

This isn't Honda's first step into mass-produced steel-aluminum structures. Last autumn it introduced friction stir welding, a mechanical system that bonds the two metals through friction and pressure rather than metal inert gas welding. The technique is being used in the 2013 Accord midsize sedan to bond steel and aluminum halves of the car's front subframe.