I use it to clean engine blocks that fail on dyno and etch the aluminum. I’m sure its not pure sodium and I am no chemist but some type of mixture added to water in a tank that has the word sodium in it.
I add the mixture in very small amounts to the water... veeeerrry slowly... like 1/2 cup at a time in 10,000 gallons of water and still get a reaction.
It’s called LYE