Letter 39017

Sulphuric acids additions via a stainless pipe [Ireland] 

January 12, 2006

I am currently looking for an alternative to 80% phosphoric acid additions for our process. 10% sulphuric will offer the same characteristic changes to the product but I query the potential corrosion issues that this may cause to stainless steel pipe lines and vessel.
Additions are made at ambient temps.

Can you advise what range of sulphuric acid concentration would be least aggressive to stainless steels.

Brid McMahon
engineer - Cork, Ireland

I can not give you a finite answer, but a 15% anodizing solution will attack even 316 SS if the temperature goes much above 75F. This is for a constant exposure. Attack increases rapidly on seams and welds as the temperature increases.
Copper, iron and chlorides will also accelerate the attack.

James Watts
- FL

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