In article , Ed Huntress
wrote:

On Sat, 20 Jun 2015 09:57:53 -0700 (PDT), Gerry
wrote:

I am working on a packaging machine that is used to package various acids in
quart and gallon plastic bottles. It will be used with phosphoric, HCl,
sulfuric and hydrofluoric acids in fairly high concentrations. The fill
nozzles are made from CPVC and are made to by-pass when the bottle gets
filled to a certain level. They are prone to breakage. I need to remake them
in a material/design that will reduce the breakage. My question is is there
a stainless alloy that would hold up to these acids?

No. Hydrofluoric will eat all stainless steels, although for
300-Series grades above 316, the problem is pitting rather than just
getting eaten away.

Hydrochloric also attacks these grades, although the effect is much
less. With most 300 grades, it eats the iron and leaves a
nickel/chrome smut.

With sulfuric, it depends on the concentration; it produces various
effects.

Stainless is not a good material to use with most acids. If you need
to use metal -- or nearly anything else -- you'd better do some
research. Here's a start:

http://www.engineeringtoolbox.com/me...nce-d_491.html

If you're tempted to look into machinable ceramics, like Macor, forget
it. They generally contain a glassy phase that is vulnerable to some
acids.

Any metal you may use will dissolve in the acid, and contaminate it.
Depending on the grade of acid, this may ruin the acid as a salable
product.

What causes the breakage? Perhaps all that's needed is more robust
physical design. And teflon is immune to most acids.

Joe Gwinn