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Baher
Member

Join Date: Jan 2009
Posts: 8

Corrosion Coupons, Minimum Corrosion Rate Calculation

11/22/2010 4:30 AM

I am preparing a procedure for using corrosion coupons on the cooling water cycle. I referred to the following references: NACE Standard PR0497, ASTM G 1, ASTM G 4, ASTM D 2688, ASTM D 2331, and NACE RP0392.

I have 2 questions:

1- What is the acceptance criteria for the calculated corrosion rates for carbon steel, stainless steel, and copper coupons.

2- What is the minimum detection limit for the corrosion rate calculations. I mean sometimes the corrosion rate equals 0.000X mpy, in most measuring methods a preset minimum value is used if the calculated one is smaller.
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cingold
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Join Date: Nov 2007
Posts: 519
Good Answers: 11
#1

Re: Corrosion Coupons, Minimum Corrosion Rate Calculation

11/23/2010 4:01 PM

I am somewhat unfamiliar with your problem but I just bought a book called Nalco Guide to Cooling Water System Failure Analysis. It hasn't come in yet but it might be helpful for your work.
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Tom_M
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Join Date: Aug 2008
Location: Calgary
Posts: 10
Good Answers: 1
#2

Re: Corrosion Coupons, Minimum Corrosion Rate Calculation

11/23/2010 4:58 PM

The answer to yoru question is of course - it depends.

Calculating the corrosion rate is usually pretty straight forward. weightloss/area/unit time.

You have to decide what is an acceptable corrosion rate. Typical values of 0.1 - 5 mpy are usually acceptable. However, you also have to look for pitting. systems may have a low corrosion rate may fail due to singular pitting.

Also in a mixed metal system you have to look at the potential for galavanic corrosion.

so like i said it depends.
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strider6
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Join Date: May 2007
Posts: 225
Good Answers: 4
#3

Re: Corrosion Coupons, Minimum Corrosion Rate Calculation

11/29/2010 4:51 AM

http://www.gewater.com/handbook/cooling_water_systems/ch_24_corrosion.jsp

http://www.chemcal.com/docs/AWT_Standards_for_Corrosion_Rates.pdf

hope this help

S

corrosion prevention
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Baher
Member

Join Date: Jan 2009
Posts: 8
#4

Re: Corrosion Coupons, Minimum Corrosion Rate Calculation

11/29/2010 5:53 AM

Thanks strider6, GE Betz book is very impressive
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