Fretting Wear

Yes — selecting incompatible metal combinations can accelerate both fretting wear and galvanic corrosion, leading to surface damage and material loss in pairings like these:

• Aluminum with Copper or Brass: Aluminum is anodic to copper, making it highly prone to corrosion when combined under vibration or mechanical load.
• Steel with Zinc or Galvanized Components: The zinc layer breaks down quickly when paired with steel under cyclic motion.
• Stainless Steel with Carbon Steel: Micromotions between these metals can trigger fretting corrosion, especially in moist or loaded joints.
• Magnesium with Other Metals: Magnesium’s extreme anodic nature makes it highly vulnerable when contacting dissimilar metals under friction.
• Steel with Bronze or Brass: Repeated micro-movement in these pairings encourages fretting wear and galvanic reactions.

Prevention tips for fretting and corrosion in mixed metals:

• Use compatible metals with similar electrochemical properties.
• Apply hard surface coatings or platings to reduce friction and isolate contact.
• Use vibration dampers, lubricants, or flexible joints to limit micro-movement.

Avoid incompatible metal pairings, particularly in parts exposed to vibration or load, to reduce the risk of fretting and corrosion.

A classic example of fretting wear is found at the interface between an aircraft’s wing and fuselage. During flight, small oscillations caused by aerodynamic forces result in micro-motion between the mating surfaces. Although minimal, this repeated movement leads to friction, surface fatigue, and the gradual removal of material.

The damage typically appears as pitting, shallow grooves, and the presence of oxide debris — often reddish or dark in color — which signals surface degradation. Over time, fretting can compromise the structural reliability of critical load-bearing joints.

How to prevent fretting wear:

• Lubrication: Apply appropriate lubricants to reduce friction and suppress debris formation.
• Surface enhancement: Use wear-resistant coatings or surface treatments to harden contact zones.
• Joint redesign: Modify interfaces to limit micro-movements and improve load distribution.

While both fretting wear and fatigue wear can lead to material failure, they stem from very different mechanical conditions and damage mechanisms.

Fretting Wear

• Cause: Triggered by small, repetitive surface movements — often between tightly fitted components under load.
• Damage: Produces surface-level wear such as pits, grooves, and oxidation (commonly referred to as fretting corrosion).
• Where it occurs: Common at splines, bolted joints, bearings, and press-fit assemblies.
• Prevention: Apply protective coatings, reduce vibration, lubricate mating surfaces, or redesign joints to limit motion.

Fatigue Wear

• Cause: Results from cyclic stress over time, even when stresses are below the material’s yield strength.
• Damage: Initiates subsurface cracks that propagate and eventually cause material separation, spalling, or full fracture.
• Where it occurs: Seen in rotating shafts, springs, gears, and other parts experiencing cyclic loading.
• Prevention: Improve fatigue resistance with better materials, reduce stress concentrations, and control operating loads.

Main Difference:

• Fretting wear is surface-based and caused by micro-motion.
• Fatigue wear is internal and driven by repetitive stress cycles.

Fretting wear can be estimated using the modified Archard wear equation, which relates the amount of material removed to contact conditions:

V = (K × F × s) / H

• V = Volume of material worn away
• K = Wear coefficient (dimensionless, depends on material pairing and environment)
• F = Normal load (force) between the contact surfaces
• s = Sliding distance or displacement amplitude (very small in fretting)
• H = Hardness of the softer contact material

Though the sliding distance s is minimal in fretting, the high frequency of micro-movements results in cumulative material damage over time.

Key Factors Influencing Fretting Wear:

• Material hardness and toughness — softer materials wear faster.
• Surface roughness — smoother surfaces generally resist wear better.
• Load and frequency — increased contact pressure and vibration cycles accelerate wear.

Reducing fretting wear often involves applying protective coatings, using lubricants, and improving design to reduce oscillatory motion. For more, see our FAQ on What causes fretting?