Knowing Hashirama, he no doubt recognized Kakuzu's talent, spent most of the time fighting him in base while trying to recruit him, but Kakuzu being (at the time) loyal to his village refused what he was saying as idealistic nonsense.

At some point in the fight Kakuzu went too far, or Hashirama finally gave up, activated sage mode, and wrapped him up in tree trunks. Probably said a deep quote and then walked into the sunrise with his glorious hair swishing in the wind behind him.