White spots inside aluminum pot?

Hello I was planning on using this 10gal aluminum pot as a sparging tank. But I notice these white spots I try using a nylon scrub brush an some dish soap but they do not want to come off here a picture of what I am talking about https://i.imgur.com/2iiKKcs.jpg.

Looks like mineral deposits left over from the last time you boiled some water. Boiling your water and decanting all except the last bit into another kettle will leave the minerals in the boil kettle to be rinsed out. Best way to reduce alkalinity of hard water and reduce the amount of acid needed to adjust the pH.

A paste of Barkeepers Friend and wad of paper towel will remove it. Let the kettle dry to reform the oxide layer after using BF.

Imbedded in the pores of the aluminum… I wonder if a boil with vinegar would pull the residue out? Everything after the mash gets boiled so it shouldn’t be a problem… Perhaps, do you acidify your sparge water? that may also help cleaning your kettle. Sneezles61

This looks like oxidation to me. If it were steel, it would be rust to give a comparison.

Its indeed oxydation. See this lots on my scuba tanks

I’m not sure I would even worry about it for a HLT. Especially if you are treating your water.