Corrosion Fatigue

What is Corrosion Fatigue?

Corrosion fatigue is a type of accelerated metal deterioration resulting from the combined effects of cyclic mechanical stress and a corrosive environment. It occurs when the combined action of corrosion & repeated loading weakens the passive film on stainless steel, initiating fatigue cracks that propagate over time.

In simple terms, corrosion fatigue describes the process in which environmental degradation accelerates fatigue damage. This phenomenon differs from standard mechanical fatigue as it involves chemical or electrochemical reactions that accelerate crack formation at the material’s surface.

Effects of Corrosion Fatigue on Stainless Steel

The effects of corrosion fatigue on stainless steel are primarily due to the breakdown of the passive film and localised corrosion at stress points. When cyclic stress is applied, small cracks form on the surface where the protective oxide layer is compromised. These cracks deepen with each stress cycle, resulting in microstructural damage and premature material failure.

Although stainless steel generally exhibits strong fatigue resistance, aggressive environments containing chlorides, acids, or high humidity can accelerate damage. Over time, the combined effects of corrosion and stress degrade the material’s performance by increasing stress concentrations and reducing its load-bearing capacity.

How Corrosion Fatigue is Detected and Assessed

Corrosion fatigue in stainless steel is detected through a combination of visual inspection and non-destructive testing (NDT). Early signs include fine surface cracks, pitting, or discolouration near welds or high-stressed areas.

Techniques such as ultrasonic testing and eddy current testing help identify subsurface or surface defects, while acoustic emission monitoring tracks crack growth in service. In laboratories, fractography confirms corrosion fatigue by examining crack patterns.

These methods help evaluate damage accurately and ensure timely maintenance of stainless steel components in critical applications.