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316SS Reactor Bolts Eaten by 170 Deg C Caustic

In a chemical process, we use stainless reactors, and the bolts & nuts are of stainless steel of 316 grade. In the process caustic is added and the temperature of the mass goes to 170 °C. What is happening is the bolts & nuts are eaten away by caustic. We thought of using Hastelloy bolts/nuts, But the cost is very high. Is there any other method to increase the life of bolts/nuts.

Durga Prasad.
- Hyderabad, India
2005

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Which grade of stainless is used for the other components, that is the items being fastened together by the bolts and nuts? Do they also suffer corrosion, or are they OK?

If they are OK, then whatever grade you are using for them would seem to be a good choice for the bolts and nuts also.

Perhaps the bolts and nuts aren't really 316, so perhaps you are getting a galvanic reaction between them and the material being fastened together.

Bill Reynolds [deceased]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.
2005

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Dear Durga Prasad
Please check the quality and confirm you are using 316SS. Procure directly from an approved Quality manufacturer.
regards

T.K. Mohan
plating process supplier - Mumbai, India
2005

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Obviously there is some chloride impurity in the caustic soda ⇦liquid caustic soda in bulk on Amazon [affil link] which with galvanic current will eat up any alloy of stainless.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2005