Study on Application Methods to Mitigate Galvanic Corrosion between Wheel Bearing and Aluminum Knuckle

The substitution of aluminum for steel is an effective weight reduction solution where the application permits it; aluminum knuckles have been widely used for this reason. However, when an aluminum knuckle is assembled with the steel outer-ring of a wheel bearing without any means for galvanic corrosion prevention, the aluminum knuckle may severely corrode. Galvanic corrosion products can make it difficult to remove a wheel bearing from the aluminum knuckle during vehicle maintenance. Prevention of this problem is the focus of this paper. In this study, several concepts were examined to prevent or mitigate galvanic corrosion between a wheel bearing and its mating aluminum knuckle. One set of concepts involves using surface treated metal sleeves (using ferritic nitro-carburizing or a special coating). The sleeves were then inserted onto the outer-ring diameters of the wheel bearings prior to assembly into the steering knuckle. Another set of concepts that were investigated involves the application of thin coatings having high anti-corrosion properties. The coatings were applied directly to the bearing outer-ring knuckle piloting surfaces and bearing knuckle mounting flange. Samples were subjected to rigorous cyclic and galvanic corrosion tests. Test results for some concepts showed mitigation of galvanic corrosion between the knuckle and bearing.