Rusty diesel tank

[Sindbad]

Today we started to clean the diesel tanks. Port and starboard tank each have a capacity of 300 lit and the aft tank 400 lit. I pumped out 20 l from the port tank and 20 l from the after tank, which was left over the winter and disposed it. Wife cleaned the port tank and it is shinning now. No rust there, only a thin layer of sludge.
Aft tank has several patches of rust flakes. I started to scratch them off, but I am afraid, I will not get everywhere, if I do this by hand.
Any suggestions?

[shakey doug]

The Missus seems to have mastered it. Your choice.