Technically you're talking about sublimation rather than evaporation. And no, it won't be very likely for the Voyagers to disappear. Most likely they will be damaged by impact or get absorbed by massive object, but sublimation at 10K will take a very very long time.

I don't have the data, but if you want to calculate the rate of sublimation, you need to look at the vapor pressure of various metals at interstellar temperatures.

Some very low numbers indeed.

But they're in interstellar space. I imagine high-energy collisions (with hydrogen atoms or loose protons) would be a more likely cause of evaporation, and I don't know the numbers for that.

If there’s 1 atom per cubic cm in interstellar space, I’m finding it takes about half a million years to collide with a mole of hydrogen (at 17km/s)

Google says that's about a gram of hydrogen. Is that enough to destroy a craft? I have little intuition, but I imagine touching a gram of 55,000-degree (Farenheit) anything would be destructive.

Will the craft be radiating heat away from itself?