CHICAGO — Honda Motor Co. Ltd. says it has developed a trio of technologies that combine steel and aluminum and is applying them to mass-produced vehicles, initially in the North American model of the Acura RLX.

The first commercial application of the technologies joins an aluminum outer-door panel—conventionally made from steel—to the steel inner-door panel, the Tokyo-based automaker said.

Honda devised new methods to prevent electrical corrosion and thermal deformation caused by the different expansion rates of steel and aluminum:

• For the outer-door panel, Honda developed a "3-D lock seam" structure, in which the steel panel and aluminum panel are layered and hemmed together twice.

• To prevent electrical corrosion, Honda used a highly anticorrosive steel for the inner panel and a new form that assures the complete filling of gaps with an adhesive agent.

• To control thermal deformation, Honda is using an adhesive agent with low elastic modulus, which allows it to stretch more readily, and optimized the positioning of the 3-D lock seam.

By combining these techniques, Honda eliminates a spot welding process that is usually necessary for joining conventional steel door panels. The methods can be applied on existing production lines, Honda said.

By using the metal-joining technologies, Honda said the weight in the steel-aluminum doors will be 17 percent less than that of all-steel door panels. Weight reduction along the vehicle’s outer body also shifts the vehicle’s point of gravity closer to its center, improving maneuverability, the company said.