salt buckets can i use?

OK so I have been keeping reef tanks for quite a while now. Brewing was a natural complement. I am figuring out that some of my equipment is dual purpose. E.g. had a refractometer for like six years and just realized on my last batch that I can use it for my beer! Lol.
Anyway the salt that I buy comes in awesome rubber gasketed buckets. Even better quality than the brew buckets I have bought. What am I looking for to (letters code etc..) to know if I can use them.
Btw if this is the case any saltwater fish store will have dozens of fresh clean empty buckets. So cheap source for new primarys

I have been keeping a reef tank since the mid 80's and have re-purposed salt buckets for quite some time. The difference between most brewing buckets and a normal bucket is that the brewing buckets are made of a food grade plastic. I don't think any salt buckets are made of food grade plastic.

I also found this explanation, note the third paragraph:

Food grade plastic does not contain dyes or recycled plastic deemed harmful to humans. However, this does not mean that food grade plastic cannot contain recycled plastic. The FDA has detailed regulations concerning recycled plastics in food packaging.

Another aspect of food grade plastic is matching the appropriate type of plastic to the food in question. Foods that are highly acidic or that contain alcohol or fats can leach plastic additives from the packaging or container into the food. As a result, you should only use plastic containers that are FDA approved for the particular type of food the plastic will come into contact with.

Finally, it should be noted that a plastic container can no longer be considered food grade if it has been used to store non-food items like chemicals, paint, or detergent.

So by repurposed does that mean brewed in them? Right now I keep my starssan in one but god I've got like ten empties. Got to imagine that they would be the picture of sanitation as I don't imagine ANYTHING surviving in the undiluted salt mix. If a drill and gasket is all thats needed to multiply my capacity tenfold then I will be pumped.
U would have to figure that salt buckets if designed at all would be made to deal with basic pH conditions.

Brand / manufacturer / model is usually stamped on the bottom.

You can call them to find out which of their buckets are fda grade.

I use them to ferment in. I have two 14.5 gallon salt containers I bought off of eBay.

reefer here too homie. im almost done with a tall oceanic bucket. ill check to see if i can use it for fermenting. Thanks for this post.

I've been using them for beer and wine for years. They work great.