Welcome to R2R! Glad you found us.
Do you, by chance, have any idea what was stored in the containers? Usually not, but figured it's worth the ask. ;-)
If they have a pickling solution smell, then that was very likely something very much like vinegar. I'd not expect that vinegar will help very much, but it also won't hurt.
What I did to clean out the tanks I have (which were "food grade", but I had no idea what was stored in them) was to rinse them out several times with tap water. Following that, I used a bleach solution (about 10:1 or so; not very strong). I let that sit for 24hrs+ and then rinsed them out again. Filled them up, and added some
SeaChem Prime to dechlorinate them. Let that sit for another 24hrs and then drained them out. I let them dry in the sun until they were totally dry inside and out. At that point, I figured they were as clean as I could get them, so put them into service.
All that was back when I was still new, so I didn't really know if it was the most efficient - or even effective - method. Still don't, really. For that reason, let's call in the rest of the #reefsquad to see if I missed anything that could help you!