A condition called ________ __________ develops on the outer surface of the inner and/or outer bearing race. A tight fit on the shaft and in the housing will prevent this from happening.

• A. surface scoring
• B. pitting corrosion
• C. blooming wear
• D. fretting corrosion

Answer: (D)

Fretting corrosion is the wear process at play here. When bearing races are not snugly fixed, tiny, repeated micro-motions occur between the outer surface of a race and its mating surface (shaft or housing) under load. Those tiny slips break the protective surface oxide and remove material in a localized band, and the accompanying exposure to lubricants, moisture, or contaminants can accelerate corrosion. The result is a characteristic surface damage—wear debris and pits along the contact area—that appears on the outer surface of the bearing race.

A tight interference fit on both the shaft and the housing minimizes those micro-motions, keeping the race firmly pressed and reducing or preventing fretting.

Surface scoring is more about abrasive scraping from particles or misalignment; pitting corrosion is electrochemical pits from corrosion alone, without the micro-motion wear pattern; blooming wear isn’t the typical term used for this bearing-face issue. So the described condition and its prevention point to fretting corrosion.