Corrosion

When discussing corrosion related to pipelines, the following key points are important to remember:

• The electrochemical process by which the iron in refined steel returns to a more stable state

• Results in metal-loss at anodic areas

• Corrosion is not uniform and homogenous

• Corrosion does not involve the application of mechanical stress

• Corrosion is a ‘stress-free’ process

Also, see these corrosion-related calculations:

1. PRCI RSTRENG and RSTRENG+
   1. One of the boundary conditions for the RSTRENG calculation is that the metal loss be from a “stress-free” process
      1. RSTRENG is therefore not valid for the analysis of dents, cracks, and other deformations
2. Pipeline Toolbox
   1. Corrosion Module
      1. ANSI B31G-1991 Evaluation of MAOP in Corroded Areas
      2. ANSI B31G-1991 Maximum Allowable Longitudinal Extent of Corrosion
      3. Rate of Electrical Current Flow Through the Corrosion Cell

      4. Relationship Between Resistance and Resistivity
         

      5. Electrolyte Resistance from Surface of an Electrode to any Distance
         

      6. Ohm’s Law of Corrosion Current
         

      7. Electrical Resistance of a Conductor
         

   2. Cathodic Protection Module

      1. Estimated Weight of a Magnesium Anode
         

      2. Resistance to earth of an Impressed Anode Ground Bed
         

      3. Rudenberg’s Formula for the Placement of an Anode Ground Bed
         

      4. Resistance to Earth of a Single Vertical Anode
         

      5. Resistance to Earth of Multiple Vertical Anode
         

      6. Resistance to Earth of a Single Horizontal Anode
         

      7. Cathodic Protection Module Attenuation Calculation
         

      8. Required Number of Anodes and Total Current Requirement
         

      9. Power Consumption of a Cathodic Protection Rectifier
         

      10. DCVG – %IR Drop
          

   3. Design and Stress Analysis
      1. Metal loss should be evaluated when performing any design & stress calculations