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• EC • Season Cracking • SSC • LME • MIC • SCC • Fatigue • Electrolysis • Stray Current • AC Corrosion • CUI • CUF • DewPoint Corrosion • Index |
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Different Types of
Corrosion
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Corrosion Under Fireproofing (CUF) |
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Recognition of Corrosion Under Fireproofing (CUF) |
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How to identify CUF? Localized CUF damage tends to occur in highly industrialized areas with high SO2 levels in the atmosphere or marine environments when operating, either continuously or intermittently, in the temperature range of 25 °F to 250 °F (–4 °C to 121 °C). When high-chloride-containing water is used to mix concrete fireproofing, metal loss can be quite severe. Some older installations involved solvent reduction (i.e. thinning) of the coating material with chlorinated solvents when the coating was applied during hot, dry weather. Some of the chlorinated solvent can remain in the dried film and produce hydrochloric acid with aging. In addition, prolonged exposure to heat at less than the design temperature may allow for the slow release of acid and subsequent corrosion. This is because the intumescent response to heat is acid activated and may not act instantaneously at the design temperature in response to a fire, typically 392 °F to 482 °F (200 °C to 250 °C).
What structures are affected by CUF? All structures with fireproofing are susceptible to CUF. Fireproofing is used on structural steel, supporting piping, and pressure vessels in process units (i.e. I-beams and skirts) to minimize the escalation of a fire that would occur with the failure of structural steel supporting piping and pressure vessels. Fireproofing is designed to extend the time it takes for structural steel from reaching 1000 °F (540 °C) and allow more time for site personnel to extinguish the fire.
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Mechanisms of Corrosion Under Fireproofing (CUF) |
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What causes CUF? Equipment and structures that operate below the water dew
point tends to condense water on the metal surface thus providing a wet
environment sustaining the corrosion process. Plants located in areas with
high annual rainfall or warmer, marine locations are more prone to CUF than
plants located in cooler, drier, mid-continent locations. |
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Prevention and Prediction of Corrosion Under Fireproofing (CUF) |
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How to prevent corrosion under Fireproofing? CUF Mitigation is best achieved by using appropriate paints/ coatings and maintaining the Fireproofing/sealing/vapor barriers. Low chloride fireproofing should be used on 300 Series SS to minimize the potential for pitting and chloride SCC. Multiple inspection techniques should be considered for cost-effective approach. How to predict dew point corrosion? Software tools such as CUI-Compass and CRA-Compass can be used to predict the risk of corrosion under Fireproofing. Click the link for details on the software.
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For more details on Corrosion Under Fireproofing |
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Where can I learn more about corrosion under fireproofing? More details on corrosion under Fireproofing are included in the following corrosion courses which you can take as in-house training courses, course-on-demand, online courses or distance learning courses:
If you require corrosion expert witness or corrosion consulting service on corrosion under fireproofing (CUF), our NACE certified Corrosion Specialist is able to help. Contact us for a quote. |
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