YogiBearMead726 has "hit the nail on the head"!
"Oil" drums, are usually mild steel. Which apart from being porous to chemicals/liquids that have a certain volatility, will also start to rust with the water content of wine.
The problem is, that certain chems/oils, can leach into the metals surface (think the inside of a truck diesel tank here - as it's a convenient analogy).
Yes you might be able to clean it enough to be able to weld the metal, but you can bet your arse, that if you filled the "cleaned" tank with water, a couple of days down the line, if you tasted the water, all you'd taste would be bloody diesel.
Which leaves you with "plastic" drums - presuming they're made of "food grade" plastic (either HDPE or PET). If they've contained anything that is any kind of solvent, then you'll get the same issue as above and anything you put in to age will get a taint of the original chemical.
So, then you're basically left with food grade plastic containers that might have originally contained something that was relatively benign and probably used in the food industry.
For instance, while "water cooler" bottles (the plastic 19 litre/5 US gallon size) are often made of "poly carbonate" - which is very slightly porous/air permeable, they can be used for fermenting etc, but if they display a stain or odour after a while, should be discarded. I wouldn't use them for long term ageing. Whereas there are the plastic "better bottles" in similar sizes, they're made from PET a.k.a. Polyethylene terephthalate, which is clear, non-porous and seems to be Ok for ageing as well as the fermentation stage of wine making.
Yes, I would say that it would be worth keeping an eye on any batches ageing in PET containers, as it's plastic and alcohol is a very good solvent. Which is why a lot of brewers/winemakers do prefer to stick with glass or stainless steel......
It's up to you what you make and age your brews in, but that lot should give you some idea about other materials......
regards
fatbloke