Normally if it's my own stupidity that damages an item I do the honest thing and just keep it for parts (i.e. I CAN'T throw it away but don't want to dishonestly warranty it) but in your case, I would contact Williams. I would expect a decent quality driver to stand up to it's "Chemical Resistant" portion of many warranties because in many peoples cases, that's a daily encounter. I've gotten generic carb cleaner on some cman driver handles and haven't noticed an issue...but that was overspray or 'blow-back'.
I remember being a kid a watching someone fix a mower...they were taking the blades off to sharpen them and I remember the words "...I really don't like doing this/don't want to do this but I guess I've gotta get it done...". A walk to the back of the garage emerging with a pipe to put on the handle of a Craftsman ratchet. "They have a lifetime warranty so if it breaks, I suppose I'll just return it..." Luckily, it didn't break but from that day I still think "right tool for the job". Still have that ratchet too...hmm THAT would be an 'out of line' lifetime warranty BUT, in your case with the driver? Again, I don't feel that's FAR out of line...
I normally catch my screwdriver handles on the soldering iron so my melted handles are quite obviously MY bad