Quest Reliability has expertise in all of the major pitting corrosion mechanisms and has solved many hundreds of corrosion problems for our industrial clients. 

Pitting corrosion is a form of localized degradation of metal that results from electrical potential differentials in a single body of metal.  Pitting corrosion can initiate in locations where compositional heterogeneity, emerging dislocations or slip steps, inclusions or contaminants, or externally induced breaks in passive or protective films occur, and different areas of the metal take on different electrical potentials.   Pitting corrosion is often one of the most destructive forms of corrosion, primarily due to the fact that it can induce equipment containment failures and undermine structural integrity with, in most cases, almost negligible weight loss.  

Failures due to pitting corrosion can be found in many different environments ranging from processing plants to residential water distribution systems.  For example:

• Carbon steel – often used as a construction material for heat exchanger tubes employed in process manufacturing (e.g., ammonia, nitric acid and sulphuric acid processes) are susceptible to pitting corrosion.  Depending on a plant’s cooling water chemistry and operating conditions, heat exchanger tubes may be subject to this form of damage.
  
  
• Stainless steels – used extensively in paper and related process manufacturing equipment.   Pitting corrosion is often associated with components that process the wet pulp mix containing chlorides and thiosulfates.
  
  
• Copper – widely used as a construction material for tubing used in potable water distribution.  Copper is normally resistant to corrosion, although under certain conditions (related to water chemistry, pH and temperature) pitting corrosion may occur on the water side of the tubing.
  
  
• Aluminum and aluminum alloys - extensively used in aerospace, automotive and building industry applications, among others. Good performance of aluminum in corrosive environments is due to a protective oxide film.  Corrosion of aluminum and aluminum alloys is commonly caused by pitting, and often induced by presence of insoluble intermetallic compounds or single elements.

For further information about Pitting Corrosion, please contact us.