Acid resistant materials

On Saturday, June 20, 2015 at 12:57:55 PM UTC-4, Gerry wrote: Rather than redesign the whole CPVC nozzle I am wondering if I can just turn the piece that fails with something stronger. Any comments/suggestions will be appreciated. TIA

My first thought is to think about using a stainless nozzle with a CPVC liner. So the acid does not touch the stainless. The stainless will eventually fail, but it might be good enough to last much longer.

Dan

Molybdenum is a possibility.

It's not difficult to machine, once you're aware of its quirks. It's quite abrasive and prone to chipping, otherwise machines much like cast iron.

Tungsten is generally more resistant than moly to acids, both hot and cold, but is considerably more expensive and not fun at all to machine.

Take this advice for what it is, a couple possibilities based on experience with the materials mentioned.

Teflon is the material. The secret to machining Teflon is a razor sharp tool bit. If you don't worry about loosing a finger every time you pick up or touch the tool, it is not sharp enough.

Teflon is the material. The secret to machining Teflon is a razor sharp tool bit. If you don't worry about loosing a finger every time you pick up or touch the tool, it is not sharp enough. ============================================================

The main thing I hate about Teflon is how it cold flows, so seals like compression ferrules eventually dig in and leak, even with regular tightening. How about virgin UHMW polyethylene? The bottles you are filling are probably PE so the chemical compatibility is there, and it is much cheaper than Teflon and doesn't cold flow nearly as much. It is softer and more flexible than CPVC but doesn't stress crack nearly as bad, so there is a good chance the life will be better. If you really need them cheap use one of those quick prototyping places and get 100-500 injection molded :-). Then just replace them often enough to keep them from breaking while filling.

----- Regards, Carl Ijames

No glass. Even borosilicate glass won't handle hydrofluoric acid.

Gunner Asch on Sat, 20 Jun 2015 14:08:43 -0700 typed in rec.crafts.metalworking the following:

Which would work for all but the hydrofluoric acid. Which eats glass, if memory serves. Fluorine compounds, go figure.

-- pyotr filipivich "With Age comes Wisdom. Although more often, Age travels alone."

Gunner Asch on Sat, 20 Jun 2015 22:16:07 -0700 typed in rec.crafts.metalworking the following:

Here's how the experimental prep of today's fragrant breath of spring starts:

The heater was warmed to approximately 700C. The heater block glowed a dull red color, observable with room lights turned off. The ballast tank was filled to 300 torr with oxygen, and fluorine was added until the total pressure was 901 torr. . .

And yes, what happens next is just what you think happens: you run a mixture of oxygen and fluorine through a 700-degree-heating block. "Oh, no you don't," is the common reaction of most chemists to that proposal, ". . .not unless I'm at least a mile away, two miles if I'm downwind." This, folks, is the bracingly direct route to preparing dioxygen difluoride, often referred to in the literature by its evocative formula of FOOF. {end quote}

A torr is Aprox 1mm of Hg ; ergo 901 torr is about 1.1 Atmosphere.

-- pyotr filipivich "With Age comes Wisdom. Although more often, Age travels alone."

tles. 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 p rone to breakage. I need to remake them in a material/design that will redu ce the breakage.

If it hasn't been suggested already, materials ARE available that won't tak e any harm. Synthetic sapphire, for instance, can be routinely made in tube for m (but it'll likely be a special-order item). Suppliers say that tubes are e asily formed. This website specifically mentions Stepaniv process for tubes:

in quart and gallon plastic bottles. It will be used with phosphoric, HCl, sulfuric and hydrofluoric acids in fairly high concentrations. The fill no zzles are made from CPVC and are made to by-pass when the bottle gets fille d 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? The part of the nozzle t hat breaks is a tube, roughly 3/8" OD with a 1/4" ID with a cone machined i nto one end and threads on the other. Rather than redesign the whole CPVC n ozzle I am wondering if I can just turn the piece that fails with something stronger. Any comments/suggestions will be appreciated. TIA

In addition to the material selections suggested by others, I'd be looking at WHY the nozzles are breaking. Perhaps you could fix this with better pos itioning or timing? I recently fixed a machine that had been giving the ope rators fits for years simply by moving a sensor to a place where it got a c leaner shot at the product going by, greatly improving the repeatablity of the system.

Of the materials selected, sapphire gets my vote as the most exotic, but UH MWPE is so friggin easy to machine...

In addition to the material selections suggested by others, I'd be looking at WHY the nozzles are breaking. Perhaps you could fix this with better positioning or timing? I recently fixed a machine that had been giving the operators fits for years simply by moving a sensor to a place where it got a cleaner shot at the product going by, greatly improving the repeatablity of the system.

Of the materials selected, sapphire gets my vote as the most exotic, but UHMWPE is so friggin easy to machine...

============================================ What are the bottles made from?