However, in many cases, corrosion may be predicted, managed, mitigated or prevented entirely by the selection of correct materials, conditions and careful monitoring.
TWI has dedicated laboratories for electrochemical and direct exposure small scale tests, larger facilities for testing specimens under load in sweet conditions, seawater (including cathodic protection), plus laboratories for H2S sour service testing.
Evaluation of materials corrosion behaviour is undertaken by relevant techniques covering rapid electrochemical testing and longer term direct exposure tests in simulated environments. Testing is in accordance with internationally recognised standards or developed by our experts in conjunction with client requirements as part of our corrosion services.
Standard test methods are also employed for routine assessments in accordance with the recognised standards for sensitisation, CPT, CCT etc. Testing of components may also involve electrochemical studies and long-term testing in purpose designed configurations.
Testing capabilities include:
- Electrochemical evaluation of materials and coatings
- Salt spray ranking assessment
- Testing of materials under load and with cathodic protection in seawater including corrosion fatigue
- Weld corrosion testing to assess weld metal, HAZ and parent material with 12-channel electrochemical weld tester for monitoring up to 12 different weldments in parallel. Monitoring of the individual weldment regions over extended periods by AC & DC test methods, plus laboratory cells and low flow conditions.
- Sour and sweet service testing for the oil and gas sector at ambient pressure or at elevated pressure and temperature in autoclaves (200 bar and 200°C) with constant and variable loads (corrosion fatigue, SSRT and ripple loading all in H2S/CO2 etc)
- Hydrogen autoclave for the study of hydrogen disbondment of weld overlays and cladding, materials embrittlement and hydrogen attack for the petrochemical, chemicals and power generation sectors.
- Full range of analytical equipment available to assess samples and specimens including SEM with EDX, EPMA, X-ray diffraction and OES, Hydrogen analysis, FT-IR with ATR, DSC etc for material chemical analysis of metals, welds and plastics
TWI undertakes all studies according to strict confidentiality and can test materials using recognised standards (ISO, ASTM, NACE etc) or specifically designed procedures using the following techniques:
Testing under load
- Testing configurations include tensile, four-point bent beam, U-bend, smooth or pre-notched geometries etc, as appropriate
- Constant-load (dead-weight) ambient and elevated pressure testing
- Slow-strain-rate testing (SSRT)
- Ripple load testing
- Corrosion fatigue (including tests in H2S)
Simulated service environments
- Sour service
- Sweet service testing
- Brines
- Seawater (natural or artificial)
- Hydrogen atmosphere at pressure
Electrochemical testing
- 12-Channel ACM Weld Tester for preferential weldment corrosion
- Crevice-free cells (Flushed port/Avesta Cells)
- Purpose-designed test cells including multiple sample test environments
- DC and AC techniques for metals and coatings
- Critical pitting temperature (CPT) and critical crevice temperature (CCT) testing
- Long-term exposure testing with LPR, galvanic current, potential monitoring and AC impedance measurement