304 SS pH Compatability @ < 5.0pH 4

[hershey28]

Food application:
Spec changing for a sugar solution from normal 7.0pH to less than 5.0pH. Is this likely to be a corrosive issue with 304 SS?

 

[unclesyd]

Normally PH 5 would be no problem.
Just to make sure.

What is the acid used to lower the PH?
How is the product going to be mixed?
What are the temperatures?

 

[hershey28]

Thanks for the reply.
This is an aqueous solution of Sorbitol, hexane-1,2,3,4,5,6-hexaol. About 70% solids. Use temp is ambient ~ 80F.

Any acidity is from the solution itself. Downstream processing includes high shear mixing with other liquids (mostly), including corn syrups, water, and liquid sucrose.

Further subsequent processing includes heat treatment and evaporation. This side of the equation is not a concern - only Sorbitol delivery itself.

 

[unclesyd]

My data shows that 304 SS is OK for your conditions.

 

[mcguire]

You could even tolerate 500 mg/l of chlorides without damaging the 304.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[Aloysius]

How does 304SS compare to 316SS for sour field service?

 

[unclesyd]

Aloysius,

You need to start a new thread in this Forum with your question. You will get a much better response.

 

[EdStainless]

Hershey, The one catch is that field welds (or poorly annealed process welds in piping or vessles) will show accelerated attack. This attack will not be very fast and it will be uniform along the welds. I have seen this in many moderately acidic systems.

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Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[unclesyd]

EdStainless,

We run very similar products, in fact a small amount of sorbitol is a impurity in the process, at a lower PH in 304L SS (old style) and 304 SS piping in our process. Some of the piping is 50 years old and we see no sign of corrosion on Sch 5 pipe.

Our process runs the slightly acidic organic alcohols and ketones from the oxidation of Cyclohexane in 304 SS and 304L SS vessels and piping. It is only when we raised the temperature and concentration of the byproduct organic acids that we start to see a problem with 304 SS and 304L SS.

 

[EdStainless]

I have seen systems running both sugar and other sweeteners show this, but yes, they were hotter. In a lot of places 'ambiant' is more like 120F by the time you add pump heating.
304L is still a reasonable solution. If there is any corrosion it will be slow. They will have plenty of time to find it and measure it before there are any problems.

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Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm