Pitting Corrosion

Fixing pitting corrosion involves several steps to remove the damaged areas and prevent further deterioration. Here are effective methods to address pitting corrosion:

1. Alloy Selection: Choose alloys with higher PREN values like 316 stainless steel for better resistance.
2. Design Practices: Optimize designs to minimize crevices and promote proper drainage to reduce stagnation.
3. Barrier Coatings: Use coatings like paints, epoxies, or Armoloy to protect metal surfaces from corrosive environments.

Preventive Maintenance:

• Conduct regular inspections to detect early signs of pitting corrosion.
• Apply corrosion inhibitors to protect susceptible metals.
• Ensure proper drainage and avoid stagnant water or corrosive deposits.

By following these steps, you can effectively repair pitting corrosion and extend the lifespan of your metal components.

Pitting corrosion is primarily a wet corrosion process. It occurs in the presence of an electrolyte, typically water containing chloride ions or other aggressive anions. The localized breakdown of the passive protective layer on the metal surface leads to the formation of small pits or cavities.

Key Points:

• Wet Process: Requires the presence of a liquid electrolyte, such as seawater, de-icing salts, or acidic solutions.
• Localized Attack: Pitting corrosion is highly localized, creating deep, narrow pits that can penetrate the metal.
• Environment: Common in marine environments, chemical processing industries, and areas with high humidity or salt exposure.

Understanding that pitting corrosion is a wet process helps in designing appropriate preventive measures, such as proper drainage, application of protective coatings, and use of corrosion-resistant materials.

Pitting corrosion is a localized form of corrosion that results in small, but deep, holes or pits on a metal surface. Here are the primary causes:

1. Chlorides: Presence of chloride ions, commonly found in saltwater and de-icing salts, can break down the passive oxide layer on metals, leading to pitting.
2. Metallurgical Factors: Inhomogeneities in the metal, such as inclusions or second-phase particles, can act as initiation sites for pitting.
3. Localized Chemical Conditions: Areas with stagnant solutions, crevices, or deposits can create localized environments that promote pitting.
4. Temperature: Higher temperatures accelerate the rate of pitting corrosion by increasing the chemical activity and diffusion rates.
5. pH Levels: Low pH (acidic conditions) can destabilize the protective oxide layer, making the metal more susceptible to pitting.

Prevention:

• Material Selection: Use corrosion-resistant alloys, such as stainless steel or titanium, especially those with higher molybdenum content.
• Protective Coatings: Apply coatings or surface treatments to protect the metal surface from aggressive environments.
• Environmental Control: Avoid stagnant conditions and ensure proper drainage and cleaning to remove corrosive agents.
• Cathodic Protection: Employ cathodic protection systems to prevent pitting in susceptible environments.

By addressing these causes and implementing preventive strategies, the risk of pitting corrosion can be significantly reduced, ensuring the longevity and reliability of metal components.