ATMOSPHERIC CORROSION
(API 570 EXAM STUDY GUIDE)
API 571 : 4.3.2 Atmospheric Corrosion
This is a common damage mechanism which happens to all the structural steel items exposed to atmosphere in our house and in industrial environment, which are not protected by surface coatings. API 571 does not gives a very in-depth analysis of this damage mechanism. It occurs every where and proper surface coating is the only way to prevent it.
Moist environment is one of the reasons for galvanic corrosion, this way atmospheric corrosion overlaps with atmospheric corrosion.
Description of Damage
Occurs from moisture associated with atmospheric
conditions
Marine environments and moist polluted industrial
environments with airborne contaminants are most severe
Affected Materials
CS, LAS and copper alloyed aluminum
Critical Factors
Physical location (Industrial, Marine, Local)
Moisture (Humidity)
Designs that trap moisture
Cooling tower mist
Presence of salts, sulfur compounds and dirt
Corrosivity:
Marine environments: 20mpy (mpy: Mills Per Year;
corrosion rate)
Industrial environments that contain acids or
sulfur compounds that can form acids: 5 to 10mpy
Inland locations: 1-3mpy
Dry rural environments: <1mpy
Corrosion increases with temperature up to 121deg.C
[250 Deg.F], after that not of any effect. This condition is not for insulated
lines.
Chlorides, H2S, flyash all accelerates corrosion
Bird turds accelerate corrosion
 |
| BIRD TURD; Refer Shutterstock for this image |
Affected Units or Equipment
Piping and equipment with operating temperature
sufficiently low.
Piping that rests on pipe supports are prone to atmospheric
corrosion
Bimetallic connections such as copper to aluminum
electrical connections.
Appearance or Morphology of Damage
General or localized depends upon whether or not
the moisture is trapped.
Metal loss may not be visually evident.
Prevention/Mitigation
Surface preparation and proper coating
application
Inspection and Monitoring
VT and UT techniques
Related Mechanisms
Corrosion Under Insulation (CUI)
This blog is not a replacement for the training provided by authorized partners/experienced institutions nor this blog guarantee success in API exams. This blog is the outcome of the approach followed by the author for the preparation of API exams.
Disclaimer: Photos are taken from different websites. If this violates any copyright rules this will be removed. Please inform me if any of the photos or contents violate copyright rules. (through 13hareesh13@gmail.com). This blog is meant for educational purposes only. If it is used for any other means without the written consent from the author, the author will not be responsible. The author does not guarantee the accuracy of the data used in this blog. All the information, data, photo/image, calculations presented in this blog should be used at the sole risk of the user. The blogger is not liable or responsible in any way for any damage, losses or costs arising from the use of the blog for any purpose whatsoever or whosoever it may be. The blog is to be used at your sole risk and responsibility.
Hope you enjoyed the quiz.
This blog is not a replacement for the training provided by authorized partners/experienced institutions nor this blog guarantee success in API exams. This blog is the outcome of the approach followed by the author for the preparation of API exams.
Disclaimer: Photos are taken from different websites. If this violates any copyright rules this will be removed. Please inform me if any of the photos or contents violate copyright rules. (through 13hareesh13@gmail.com). This blog is meant for educational purposes only. If it is used for any other means without the written consent from the author, the author will not be responsible. The author does not guarantee the accuracy of the data used in this blog. All the information, data, photo/image, calculations presented in this blog should be used at the sole risk of the user. The blogger is not liable or responsible in any way for any damage, losses or costs arising from the use of the blog for any purpose whatsoever or whosoever it may be. The blog is to be used at your sole risk and responsibility.
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