Switch contact material rating - use 120 V AC rated with low DC ?

When breaking inductive circuits with a DC supply (like a relay) there will be a spark generated that burns the contact material. Some switches have very small opening of the contacts when off, and the spark may not go out for some time on DC. On AC, the reversal of the voltage gives the spark time to de-ionize every 8 ms. This has nothing to do with continuous operation with the contacts closed, but os all about breaking the circuit while current is flowing.

Yes, it is unlikely that this kind of spark damage would occur on such low voltage and current. But, a silver contact may tarnish when left off for a long time, and may fail to "close", ie. break through the oxide, the first time it is operated. that may, or may not, be a big concern in your project. That is the advantage of the gold contacts, they can be left open for yests, and work the first time they are activated.

Jon

There's a pretty good explanation of "dry switching" here:

Hope This Helps! Rich