Corrosive environment: 24 VDC vs 110 VAC.

Hi all,
If you are in a corrosive environment, are 110 VAC devices (like relays, contactors, you name it) a better option than the 24 VDC equivalents?

Thank you!

It depends on the corrosive environment. I would look more toward the material that the device is made out of.
Example - Gold contacts on the relays can provide good results in corrosive environments.

Just a thought,

Elcan,

In corrosive environments, you MUST look at everything.

1. what chemical(s) / mixture of chemicals are present?
2. select all components for your job. sensors, so cord grips, conduit, enclosure(s), enclosure purge / pressurization, wire and insulation type, enclosure components, and so on.
3. look at the chemical reactivity of these components and see if they are compatible. if they're not, select another device.
4. do you need seal off's to keep the chemicals out of the enclosure?
5. can you put the enclosure(s) in a safe area and use seal off's?

in a corrosive work area, DETAILS MATTER !

A mechanical designer changed my stainless steel order on a tank just to save $2k, and the acid eat the material within a week, leaked acid everywhere and we had to foot the cleanup bill plus the time and material to replace the tank.
The material requirements were on the design prints and the po to the steel company.
the boss was not a happy camper, especially when he found out the correct materials got changed.

regards,
james

Higher voltage devices might work better, because they will tolerate losses from corroded contacts better, but that's hardly the first consideration.
24 DC, because the stuff we build today is safe.

Look for stuff rated for outdoor and wet environments. PCB's will have conformal coatings, boxes will have O'ring seals, etc. Use plastics/fiberglass instead of metals where possible.

Add N2 purge to enclosure. CDA if N2 is impossible.

Thanks everybody for the comments!
My question was in general, not for a particular environment.
There's no much literature on the subject online. Actually, the only piece of info I've found so far is in this same forum (see reply #4):
http://www.plctalk.net/qanda/showthread.php?t=73986&highlight=corrosive+24vdc

I use 24VAC on digital I/O runs in wet environments. Its still safe but doesn't provide the fixed polarity that promotes copper wire turning into that pretty blue copper powder.

I have to interpose relays in the PLC cabinet because 24vac IO is difficult to find, but I like the relays anyway so I'm OK with that.