Summary for pvc vs cpvc Discussion
PVC vs CPVC for alkaline zinc nickel process is mainly a temperature question. John Stevenson asked whether PVC or CPVC should be used on an alkaline zinc-nickel process. In the reply, the answerer said PVC and CPVC have equal chemical resistance, but CPVC costs more and tolerates higher temperatures. He noted that PVC is commonly considered suitable up to about 140 °F, though piping that can sag may need a lower practical limit. For the alkaline zinc-nickel plating bath itself, he said PVC would likely be plenty safe because most such processes run near ambient temperature. However, for other parts of the line such as cleaners and hot rinses, he advised against PVC and recommended CPVC or another higher-temperature plastic for piping, pumps, tanks, and filters.
Q. Should we be using PVC or CVPC on an Alkaline Zinc-Nickel process?
John Stevenson
– Clifton Springs, New York
June 1, 2020
A. Hi John. PVC & CPVC have equal chemical resistance but CPVC is significantly more expensive and offers higher temperature resistance. It’s hard to say the exact temperature limits because the materials gradually soften with temperature rather than exploding at an ignition temperature 🙂
But in general people talk about the limit for PVC being roughly 140 °F (sometimes they say 150 °F for tank linings for the reason I mentioned), so for piping that could sag, probably a bit less. I’m not quite sure what you mean by the “process”. My understanding is that most alkaline zinc-nickel plating processes operate at not much above ambient, so PVC would be plenty safe. But if you’re talking other steps in the process like cleaners and hot rinses, I would not use PVC there; you would want the piping, pumps, tanks, filters, and whatever, to be of CPVC or some other higher temperature plastic than PVC.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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June 2020
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