316 stainless steel versus sodium chloride traces 2

[RLT]

We have a batch process operating at a temperature of 180C and a pressure of 5 bar and where one of the components is sodium hydroxide. Actually, we purchase solid sodium hydroxide and dissolve it manually. We are intending to purchase dissolved sodium hydroxide (50%) but we were informed that this product has traces of sodium chloride. Which is the maximum allowed concentration of sodium chloride that will not affect our equipment which is made of 316 stainless stell?

 

[Surin]

Corrosion in chloride environment for 316 SS is usually in the form of stress corrosion cracking (SCC). Important factors (besides residue stress) are chloride and dissolved oxygen. High temperature will accelerate the process by creating local concentratation of chloride at surface of the vessel. I do not have particular info for your case but any chloride concentration in the range of 100 ppm or above should be avoided.<br>
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Hope this will give you some guid line.<br>