If they don't have any premask (application tape) on them yet, I'd suggest having them coldsealed (mechanical lamination using a self-adhesive polyester material).
You may be able to have them wetsealed (a roller application of a liquid sealer), but I'd check a sample first to make sure it won't give you any trouble with the ink bleeding, etc... first.
You could also use a spray topcoat after they are applied.
Again be careful how much you spray, or you may rewet the ink, and cause it to bleed.
I'd do it in very thin layers to start, and then thin layers from there.
Once you get a few of the very thin layers on the ink, they should protect it from the thin layers.
The cold seal is going to be the best option, but will probably be the most expensive as well.
Polyester (Mylar) is very chemical/water resistant.
We use it at work for industrial labels that are going on hydraulic equipment, etc...
It is much more durable than the vinyl as well, and will hold up to moderate abrasion with only minimal surface scratching.