Padlock keyhole clogged with sand/salt?

I'm voting for a quarter pound of C-4.

 

C-4 should only be used in full pound increments.

 

Easiest way to handle it, do not lock it trailers. I normally put a seal on the trailer, if I lock it I pull the lock before I start out for the trip.

 

Don't overdo it....

 

Jeez! We used to carry a jack, lugwrench and a spare tire. Well the spare had a cable and padlock on it. Nothing worse than getting a flat and getting the wheel off only to find you couldn't get the lock off the spare! Best way to do it was to make sure you could get the lock off before you took anything apart.
Eventually we started dipping the locks in Plas-ti-kote to protect them

 

Forget C4, way too clean. I would unhook from the trailer and get a run at it with your tractor. Get her up to about 7th gear and just slam the hell out of that trailer wherever the lock is. Wear your seatbelt. You're not stupid after all. Show that lock who's boss! Don't forget to log Personal Conveyance before you do this, your truck will be not be moving freight so you need to get that part right or you could risk dire consequences with the law.

 

Break free (or something that will dry pretty quickly) with a can of compressed air (lube and clear, lube and clear, etc...) once that is done get you some powdered graphite to loosen up the internal guts, then once it's clear keep it covered for future use.

WD40 will leave a residue that you will not be able to get out and since it's a penetrant and not a true lubricant, if the internals of the lock are starting to rust, WD40 will make it worse in time.

I have used something like this with my locks. To include a very rusty spare tire lock.
3-IN-ONE 2.5 oz. Lock Dry Lubricant Oil-120074 - The Home Depot

 

My new KW T680 came with locking fuel caps. Didn't think much about them until my first trip through Oregon where they use crushed lava rock instead of salt for ice and snow. When I finally managed to get them both open, I disabled the locks so they will no longer work.

 

soak with pb Blaster and heat/torch. If you can get straw inside and spray pb blaster inside lock to point where it fills up thats would be best.