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Microbiologically Induced Corrosion (MIC) mitigation for wet layup

Microbiologically Induced Corrosion (MIC) mitigation for wet layup

Microbiologically Induced Corrosion (MIC) mitigation for wet layup

(OP)
I am subcontracted to a company that is looking to do a wet layup of a stainless steel condenser at shutdown.  It has been suggested to provide a wet lay-up with inhibited water containing 0.01 M sodium hydroxide (pH=12) after each shutdown, with a down time not to exceed one year.
 
Condensate from the last campaign indicated a maximum chloride concentration of 0.3 ppm, a maximum fluoride concentration of 0.2 ppm and a pH>9.  The elevated process condensate pH has been attributed the the presence of ammonia.  The shell side temp is 50 C at a pressure of 60 torr (vacuum).  On the tube side, the max inlet temp is 21 C and max outlet temp is 32 C.  The raw water use for cooling on the tube side is expected to have a chloride concentration of <25ppm.
 
At the current chloride levels, temperature, and pH, the SS condenser is expected to exhibit excellent corrosion resistance, leaving the concern of MIC.  Will a wet layup with 0.01 M NaOH prevent MIC?  Is this type of a wet layup a standard industry practice for controlling/mitigating MIC?  

Your help is appreciated,
mfeldmann

RE: Microbiologically Induced Corrosion (MIC) mitigation for wet layup

Dunno what practice is standard, but bacteria don't seem to like a pH much over 9 or 10.  Some of them can live quite well in weak battery acid solutions, but not alkaline.

I think you'll be OK if you can avoid evap. which will concentrate the Cl.  You also might consider a non-Cl biocide to sterilize things.  If so, make sure the manuf. know your intended pH!

What's the tubing-304?

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