1. Field of the Invention
The present invention relates, generally, to a magnesium alloy member, and particularly to a magnesium alloy member superior in corrosion resistance.
2. Discussion of the Related Art
Magnesium alloys have been attracting attention as having a number of excellent practical properties for use as structural materials. Magnesium is practically lighter, stronger, and stiffer than iron and aluminum. Magnesium alloys have highest capability in absorbing vibrations (damping capacity) among popular metal materials (Fe, Al and so on), highly resistant to dint, less likely to deform with time or temperature, and easily recyclable. For these reasons, magnesium alloy is suitable as structural material for vehicles and for housing of portable terminals.
Because magnesium alloy is the most common popular alloy, when screwed or fastened together with different metals such as iron and aluminum, electrolytic corrosion is likely due to moisture in electrolytes in rain, melted snow, salt, etc. In particular, inside the hood and on the inside surface of the body of automobiles, electrolytic corrosion happens more frequently due to the electrolytes. Electrolytic corrosion may cause fastened parts to be come loosened/detached.
Referring to FIG. 5, a typical AZ91D magnesium alloy sheet 12 and a metallic sheet 14 are fastened with a steel bolt 16 and a nut 17 between three aluminum washers 18. In order to decrease electrolytic corrosion between the magnesium alloy sheet 12, the bolt 16 and the washers 18, the washers 18 may be insulated by anodic oxidation, or, the steel bolt 16 may be coated with resin. However, performing anodic oxidation on the washers 18 is very expensive, and the bonding strength and durability on resin coated steel bolts 16 is weak.
What is needed, therefore, is a new magnesium alloy member that can decreasing electrolytic corrosion when contact with different metals. A method for making the new magnesium alloy is also desired.