Corosion resistant materials to sodium hypochlorite

[Spike42]

I am designing some inspection equipment for a bleach bottling plant (sodium hypochlorite) and I am looking for a clear plastic material that will survive the enviroment. The plastic material will be used to house some camera equipment and so must remain optically clear. I already have speced out using either PVC coated or powder coated steel insted of using stainless steel (our useal standard). Our other plastic components are manufactured out of UHMW, delrin, or PBT and I don't care if they discolor over time, but I am worried about my camera housing. I would like to use a plactic material if possible over glass but will use glass if there is no other options. Thanks!

 

[unclesyd]

My literature only mentions Polyethylene and PVC as a thermoplastic for use with sodium hypochlorite.

We used large clear plastic panels around a process that we once operated. The panels were exposed to HCl fumes and at times Cl fumes and it stood up very well. It may have been a simple as plexiglass or as exotic as polycarbonate.
I'll try to find out what the material was. There was a lot of it so it had to be inexpensive as they didn't spend money in that area.

 

[Spike42]

That would be great if you could find out. I am not worried about contact to the chemicals themselves (possible but not likely) just damage from the fumes.

 

[moltenmetal]

Polycarbonate should be fine as a transparent enclosure material in a non-wetted application like this. It's less likely to crack than acrylic.

 

[Spike42]

My plastics vendor mentioned "clear PVC". I did not know that that even existed untill now. does anyone have any experience with using it?

 

[unclesyd]

Spike42,
The material is plexiglass and is mounted with glass reinforced plastic screws.
Don't not use metal screws, especially any ones with copper, if at all possible.

You will have to watch the focus of your camera as plexiglass with play tricks with the light. There is a coating that will correct this problem.

 

[jdarco]

I'm not familiar with "clear PVC" in a sheet type product, but am familiar with it in piping. It actually has a bluish tint and will discolor in sunlight! If the sheet your supplier is referring to is the same resin, I doubt it will meet your needs. Transparent would be a better description!

 

[moltenmetal]

Agreed. The clear rigid PVC sheet and pipe I've seen has a bluish tint and a tendency to yellow with time. It's also far from transparent- translucent would be a better description. That said, I've got a very nice corrugated transparent PVC roof over a portion of my back deck- it gets heavy sunlight exposure and has remained crystal clear for the past four years. But I've never seen optically transparent rigid PVC sheet. I've seen lots of nearly-transparent flexible (plasticized) PVC material. Same tendency to yellow over time, though, and not much good as a window material.

Stick with polycarbonate. Readily available, craze and crack resistant, and beautifully optically transparent. Agree with the other comments, though- a window of any kind can wreak havoc with auto-focus devices on some cameras.

 

[Spike42]

Having the camera looking through a window of some sort is not a problem, I have used acrylic many times in the past for this pourpuse. My plastics guy is sending me samples of several materials for testing. I figure I will just soak the pieces in a solution of sodium hypochlorite and see which material holds up the best over time.

Question on the yellowing: is it just UV wavelengths of light that cause this or is it somthing else? Thanks!

 

[moltenmetal]

The UV is worst, but I've seen yellowing over time of some of these PVC products even in normal industrial lighting environments. There's some UV in industrial lighting, but not all that much relative to sunlight.

 

[joeswoes]

If you want long life impervious to UV and chemical ,then use FEP fluoropolymer. Not as transparent as glass or polycarbonate, but probably comparable to PVC