SS 304 / Glycol corrosion resistance

[asv80]

Does SS 304 have good corrosion resistant in glycol service? The references I checked say they do, but we have an instance where SS 304 glycol heater has split tubes in less than 3 months service and also shows signs pf pitting.

Has anyone seen this type of attack before?

Thanks in advace.

 

[EdStainless]

I have seen similar attack in poorly maintained glycol systems. Degredation of the glycol and the presence of impurities can cause severe problems.
What is the temperature of your system?
Were the split tubes investigated? Is it CSCC?

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Rust never sleeps
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[gr2vessels]

asv80,
Out of curiosity, what is the "glycol system" you have mentioned. The glycol is a corrosion inhibitor used for the protection of carbon steel "systems", let alone stainless steel tubes.
There must be something else in the system, like water with dissolved chlorides, CO2, dissolved oxigen or other impurities. Since you mentioned a heater, I also assume high enough temperature, for the "impurities" to atack the badly welded seams, the short cold bent elbows without heat treatment and other stressed components.
These are only a few considerations of many other possible, out of which the most improbable one is the glycol itself.
Give us some details of your process.
gr2vessels

 

[asv80]

The system is 25% glycol and 75% fresh water and it being heated to about 190 deg F. The split in the tube looks like a stress corrosion crack.

 

[stanweld]

Glycol is primarily used in water cooling solutions/systems as an anti freeze compound. Corrosion inhibitors are added to provide corrosion resistance. Alone, Glycol will not provide protection from CSCC when chlorides are present in the water and at 190 F you can bank on CSCC if they are sufficiently present.

As Ed has stated glycol (and corrosion inhibitors) may break down at higher temperatures forming weak acid compounds. I had this problem once and the pH of the cooling water solution approached 2.7; no stainless in that system but plenty of carbon steel corrosion.

 

[EdStainless]

My guesses,
1. Inhibitor failure, not enough or too old.
2. Glycol decomposition and resulting low pH
3. System was not real clean, water used was not real clean either. Flush system with clean DI water and use DI for system refill.

There are inhibitor test kits that should be used regularly.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[asv80]

What happened to my previous post!?

Anyway, thanks guys. We are going to check the glycol system.