Corrosion testing and measurement

• Purpose:

  1. Planning design
  2. Development of corrosion-resistant mat and protection method

  Therefore quantitative and qualitative
• Principles:

  Reliability- reasonable- represents most possible corrosion

  Reproducibility- accurate- can we trust?
• Types of Tests:

  1. Lab tests (accelerates)

  • condition can be severe
  • useful but not same as working situation
  • stimulated environment/conditions

  2.Pitot plant or semi-works

  • Small scale prototype
  • actual mat,temp,chem
  • data for design

  3.Actual plant (field tests)

  • test in real plant operation
  • for evaluation & improvement
• Tesing Methods:

  1. Exposure tests to measure mass loss- suitable for general corrosion
  2. Special evaluation- localized corrosion

  • SCC test: U bend specimens with bolt
  • slow strain rate test (SSRT)

  3. Electrochemical measurements- fast lab tests

  4.Corrosion products: characterization and microanalysis for corrosion mechanism studies
• 3. Electrochemical measurements- fast lab tests

  1. Use polarization curve

  • current is easy to record
  • corrosion is hard to measure therefore relate current to corrosion

  2. Impedence mapping

  • impedance=resistance to power
  • coating with artificial defect on top after exposure
  • dark blue= decrease impedance, decrease corrosion resistance

  3.SVET

  • microelectrochemical technique
  • can measure micro/anodic/cathodic position & current density- corrosion rate