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Corrosion of SS316 in 1.2 pH buffer solution

I used a stirrer of passivated SS316 material for stirring to the chemical pH1.2 buffer solution. It gets blackish and rough in just half an hour. Why? and what will be the solution?

Prasad Oke
Q. C. Incharge - Mumbai, Maharashtra, India
December 2, 2008

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First of two simultaneous responses --

Though resistant to many environments, SS316 is not immune to every chemical. Most certainly your buffer contains chlorides. Use a plastic stirrer instead.

Guillermo Marrufo
Monterrey, NL, Mexico
December 3, 2008

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Second of two simultaneous responses -- December 3, 2008

That is a very acid material and 316 SS will have a tough time existing in it, especially if the solution has ANY chloride, fluoride or iodide in it.
On top of that, it is a mixer so will have constantly refreshed acid in the "difusion layer".
I would look at a very heavy (multiple) coat of teflon or a cheaper route would be a good coat of plastisol which most plating rack makers could do for you. The plastisol will cause a slight loss of mixing efficiency as it is a considerably more bulky material.

James Watts
- Navarre, Florida