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Corrosion of SS-304 in Vinyl Chloride service with MoistureHelpful Member! 

rtsd (Materials) (OP)
30 Jan 12 7:10
We have SS-304 pipeline to handle the recovery of Vinyl Chloride from PVC reactor, it has moisture causing HCL, there is no problem with SS-304 pipeline but Ball Valve of SS-304 installed on this line having corrosion.

Kindly guide how to overcome this problem either by material upgradation or by changing valve type from Ball to Plug or other.
MortenA (Petroleum)
31 Jan 12 2:40
You dont mention the type of corrosion that you encouter - is it indeed chloride stress corrosion or? For those of us not familiar with the process, is it a liquid (with water)? Is your pipe a material 304 or is it 304L?

Best regards

rtsd (Materials) (OP)
31 Jan 12 10:08
yes Vinyl Chloride is in liquide form and the there is uniform corrosion of ball and seat of ball valve of SS-304/304L.
Pitting corrosion is the type of corrosion.
Helpful Member!  MortenA (Petroleum)
2 Feb 12 1:48
SS are suseptible to pitting corrosion when in precense of chlorides. The solution seems to go for more molybdenum - but all SS can experience pitting. The fact that its the valve and not in the pipeline lead me to suspect that the pipeline has a good protective film whereas the valve dosnt. Theres nothing that can be done about that as such. A valve with a protective coating on the surfaces as well as another valve type may be a solution? Here you should take to the valve vendor.

Best regards Morten
EdStainless (Materials)
12 Feb 12 12:47
Is it only the ball that is corroding?
If so try to look for a replacement set of valve trim with a ceramic ball.
I would stay with a ball valve, unless you can't find the trim in which case a plug valve might be a good option.

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