caustic corrosion

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caustic corrosion

Postby farhad.dan » Sat Jun 16, 2012 11:15 pm

does caustic corrosion occur at room temperature?
there is an idle super heater. In one of its horizontal tubes two identical parallel trench or depressions exist. under and above the trenches dense magnetite and porous orange hematite scale is formed respectively. P , K, and trace amount of Na, is detected by EDX in the trench scale. my problem is: most of the details about caustic corrosion in literature is about caustic embrittlement. i attribute the damage to: concentration of contaminants at the waterline due to surface evaporation and formation of harsh caustic media at the waterline. But i wonder if even this caustic media can cause this localized wall thinning at room temperature?!
tnx a lot
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Re: caustic corrosion

Postby farhad.dan » Sat Jun 16, 2012 11:15 pm

farhad.dan wrote:does caustic corrosion occur at room temperature?
there is an idle super heater. In one of its horizontal tubes two identical parallel trench or depressions exist. under and above the trenches dense magnetite and porous orange hematite scale is formed respectively. P , K, and trace amount of Na, is detected by EDX in the trench scale. my problem is: most of the details about caustic corrosion in literature is about caustic embrittlement. i attribute the damage to: concentration of contaminants at the waterline due to surface evaporation and formation of harsh caustic media at the waterline. But i wonder if even this caustic media can cause this localized wall thinning at room temperature?!
tnx a lot
farhad.dan
 
Posts: 4
Joined: Sat Jun 16, 2012 10:45 pm
Occupation: MSc student
Project Question: corrosion
Project Due Date: n/a
Project Status: I am finished with my experiment and analyzing the data

Re: caustic corrosion

Postby amyc » Mon Jun 18, 2012 8:54 am

Hi - I am moving your post to the Physical Science forum, rather than "Careers in Science."

Please be aware that the Ask an Expert forums are available, specifically, for students and families working on K-12 science projects.

Amy
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Re: caustic corrosion

Postby John Dreher » Mon Jun 18, 2012 11:58 pm

does caustic corrosion occur at room temperature? . . .


The full question is far over the technical level of a K-12 education site such as ours. You might get lucky -- some of our volunteers have wide ranges of expertise, but as an astrophysicist I have little to contribute except a general impression that the answer is "yes" after scanning the first dozen results that popped out of Google when the above phrase was entered in the search field.

Also, try posting to a chemical engineering site, for example

http://www.cheresources.com/invision/fo ... essionals/

Sorry that I could not be more helpful.
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Re: caustic corrosion

Postby farhad.dan » Wed Jun 20, 2012 11:57 am

John Dreher wrote:
does caustic corrosion occur at room temperature? . . .


The full question is far over the technical level of a K-12 education site such as ours. You might get lucky -- some of our volunteers have wide ranges of expertise, but as an astrophysicist I have little to contribute except a general impression that the answer is "yes" after scanning the first dozen results that popped out of Google when the above phrase was entered in the search field.

Also, try posting to a chemical engineering site, for example

http://www.cheresources.com/invision/fo ... essionals/

Sorry that I could not be more helpful.


tnx a lot, i hope the site you mentioned would help me
farhad.dan
 
Posts: 4
Joined: Sat Jun 16, 2012 10:45 pm
Occupation: MSc student
Project Question: corrosion
Project Due Date: n/a
Project Status: I am finished with my experiment and analyzing the data

Re: caustic corrosion

Postby Craig_Bridge » Wed Jun 27, 2012 5:01 pm

Consider the possibilities of cathodic errosion. Cathodic errosion happens over a wide temperature range. Any small direct current flow in the wrong direction will cause metalic errosion and its effects will be strongest at boundary conditions that concentrate the current density. Cathodic protection has long been used for underground steel pipelines and in chemical processing plants to make sure that the electron flow is such that plating rather than annode sacrifice occurs wrt to the metalic pipe. This is also the reason why water heaters have magnesium sacrificial annodes in them to protect electric heating elements and other metal surfaces from cathodic errosion.

There are other possibilities that need to be investigated if it turns out appropriate cathodic protection exists; however, you haven't provided enough details of the materials and environment to give you any other hints.
-Craig
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